
Class JIL£j.^2J 
Book ,<> G . 



COPYRIGHT DEPOSIT. 



RUBBER HAND STAMPS 



AND THE 



MANIPULATION OF RUBBER 



A PRACTICAI^ TREATISE ON THE MANUFACTURE OF INDIA 
RUBBER HAND STAMPS, SMAI,I^ ARTlCIvES OF INDIA 
RUBBER, THE HEKTOGRAPH, SPECIAI, INKS, 
CEMENTS, AND AI^I^IED SUBJECTS 



ALSO 



Giving the Sources of India Rubber and Its History— Its 

Collection— Properties of Unvulcanized and Vulcanized 

Rubber— THE Manufacture of Masticated, Mixed jsheet, 

and Vulcanized India Rubber— Various Vulcanizing 

AND Curing Processes -the Solution of India 

Rubber— Ebonite— Vulcanite, Gutta Percha, 

Etc., Etc., Etc. 



BY 

T. O'CONOR SLOANE, A.M., E.M., Ph.D. 

Author of " Arithmetic of Electricity," "Electricity Simplified," 
"Standard Electrical Dictionary," etc. 



FULLY ILLUSTRATED SECOND EDITION 



NEW YORK 

NORMAN W. HKNIvEY & CO. 

132 Nassau Street 

1900 



TS 



^ ( 



Two Copies t^ecejy^jd 
APR 14 1905 



\^bO 



Copyright, 1890, by 
NORMAN W. HENLEY & CO. 



y 




^ 



PREFACE 



The present work hardly needs a preface. The 
object is to present in the simplest form the subject 
of the manipulation of india rubber. To mould 
and cure the mixed gum but few appliances are 
needed^ and these can be made at home. The arti- 
cles produced are of more than ordinary utility. 
These two facts give value to the art and furnish a 
raison d'etre for this book. If its instructions do 
not prove practical it will have missed its object. 

For some reason the methods of moulding the 
material are not generally known. ^ Experiment has 
taught many the futility of attempting to melt and 
cast it. While thus intractable by the usual meth- 
ods, it is the most plastic of materials when prop- 
erly treated. Its power of reproducing the finest 
details of a mouldy of entering all the intricacies 
and undercuttings of a design, cause one to feel a 
peculiar pleasure in working with so responsive a 
material. It is not saying too much to affirm that 
to some readers this book will disclose a long hidden 
secret. To make it more generally useful it is writ- 



iv P HE FACE. 

ten for such readers, to meet the want of those 
knowing of the subject. It was 'felt that in follow- 
ing this course, and in treating the subject from its 
first steps, including the simplest as well as most 
advanced methods, the book would appeal to a 
larger body of readers. 

The allied subjects to which some chapters are 
devoted will be acceptable to many readers. The 
hektograph is given in several modifications. A 
substitute for rubber stamps which stands the 
severe usage of the Post Ofiice has very distinct 
merits, and the manufacture is accordingly 
described in detail. Cements and inks embody 
many special formulae. In the last chapter inter- 
esting and practical notes will be found. 

For the use of certain cuts we are under obliga- 
tions to the Buffalo Dental Manufacturing Co., 
Messrs. E. & F. N. Spon & Co., and to Mr. L. Spang- 
enbergo 



CONTENTS 



PAGE 

CHAPTER I. 

THE SOURCES OF INDIA RUBBER AND ITS HISTORY, 

The Trees — The Sap — Caoutchouc — Early Uses by 
the Indians— First knowledge of it in Europe — Good- 
year, Day, and Mackintosh 9 

CHAPTER 11. 

THE NATURAL HISTORY AND COLLECTION OF INDIA 

RUBBER. 

African, East Indian, Central and South American 
Gums — Different Methods of Collection and Coagula- 
tion 15 

CHAPTER III, 

PROPERTIES OF UNVULCANIZED AND VULCANIZED IN- 
DIA RUBBER, 

Properties of Unvulcanized Rubber; its Cohesion and 
importance of this property — Analysis of Sap and 
Caoutchouc — Effects of Heat and Cold — Distillation 
Products — Vulcanized Rubber, and its Properties., 24 

CHAPTER lY. 

THE MANUFACTURE OF MASTICATED, MIXED SHEET 
AND VULCi^NIZED INDIA RUBBER. 

Treatment by the Manufacturer — Washing and Sheet- 



vi CONTENTS. 

ing— Masticating — Making Sheeting and Threads — Mix- 
ing — Curing — Coated Tissues 35 

CHAPTER y. 

INDIA RUBBER STAMP MAKING. 

Mixed Sheet — Outlines of Moulding — Home-Made 
Yulcanizing Press — Further Simplifications of Same — 
Securing Accurate Parallelism of Platen and Bed— Dis- 
tan-ce Pieces — Wood vs. Iron as Material for Press — 
Use of Springs on the Home-Made Press — Metal Flask 
Clamps — Large Gas-Heated Vulcanizing Press — Prepar- 
ing Type Model — The Matrix — Plaster of Paris and 
Dental Plaster as Substances for Matrices — Dextrine 
and Gum Arabic Solutions for 'Mixing Matrix — How 
Matrix is made — Shellac Solution for Matrix — Matrix 
Press and Spring-Chase — How to retard the Setting of 
Plaster of Paris — Oxychloride of Zinc Matrices — Talc 
Powder — Moulding and Curing the Stamp — Kerosene 
Heating Stove — Manipulation of Press — Degree of Heat 
— Simple Test of Curing — Time Required — Combined 
Matrix Making and Yulcanizing Apparatus — Chamber 
Yulcanizers — Object of Steam in Yulcanizers — Temper- 
a,ture Corresponding to Different Steam Pressures — 
Jacketed Yulcanizers — Gas Regulator — Flower Pot 
Yulcanizer — Fish Kettle Yulcanizer — Making Stamps 
without any Apparatus Whatever — Notes on Type, 
Quadrats and Spaces — Autograph Stamps 47 

CHAPTER YI. 

INDIA RUBBER TYPE MAKING. 

Movable Type Making — Simple Flask and Matrix — 
Precautions as to Quantity of Rubber — Moulding — 
Curing — Cutting Type Apart — Special Steel Moulds — 
Wooden Bodied Type 73 



CONTENTS, vii 

CHAPTER YII. 

THE MAKING OF STAMPS AND TYPE FROM VULCAN- 
IZED INDIA KUBBER. 

Ready Vulcanized Gum as Material for Stamps — 
Simplicity of the Process of Usint^ it — Advantages 
and Disadvantages — Availability for Type 77 

CHAPTER YIII. 

VARIOUS TYPE MATRICES FOR RUBBER STAMPS AND 

TYPES. 

Electrotype Matrices — Papier Mache — Flong Paste — 
Elong Matrices — Beating into Model — Drying and Bak- 
ing — S truck-up Matrices— Chalk Plates 80 

CHAPTER IX. 

THE MAKING OF VARIOUS SMALL ARTICLES OF INDIA 

RUBBER. 

Suction Discs — Pencil Tips — Cane and Chair Leg 
Tips— Corks— Mats — Cord and Tubes— Bulbs and Hol- 
low Toys . . . o o o 85 

CHAPTER X. 

THE MANIPULATION OF SHEET RUBBER GOODS. 

Sheet Rubber Articles — Toy Balloons — Uses of Sheet 
Rubber in the Laboratory 94 

CHAPTER XL 

VARIOUS VULCANIZING AND CURING PROCESSES. 

Liquid Curing Baths — Sulphur Bath — Haloids and 
Xitric Acid as Yulcanizers — Alkaline Sulphides — Sul- 
phur Absorption Process — Parke's Process 97 

CHAPTER XIL 

THE SOLUTION OF INDIA RUBBER. 

Mastication with Solvent — Peculiarities of the Pro- 



viii CONTENTS, 

cess — Different Solvents and their Properties — Paraflfin 
—Vulcanized Rubber Solution — Aqueous Solution 103 

CHAPTER XIII. 



Ebonite and Vulcanite — Manufacture — Manipulation 
— Gutta-Percha and its Manipulation 108 

CHAPTER XIV. 

GLUE OR COMPOSITION STAMPS. ' 

Substitute for Rubber Stamps — The United States 
Government Formula — Models and Moulds — Dating — 
Handles 113 

CHAPTER XV. 

THE HEKTOGKAPH. 

How Made — The French Government Formula — Hek- 
tograph Sheets 121 

CHAPTER XVL 

CEMENTS. 

Marine Glue, and other special Cements 125 

CHAPTER XVII. 

INKS. 

Hektograph, Stencil and Marking Inks — White and 
Metallic Inks 129 

CHAPTER XVIII. 

MISCELLANEOUS. 

Preservation and Renovation of India Rubber — 
Burned Rubber for Artists — India Rubber Substitutes 
— General Notes of Interest 134 



RUBBER HAND STAMP MAKING 

AND THE MANIPULATION 

OF RUBBER. 



CHAPTER I. 

THE SOUKCES OF IKDIA RUBBEK AKD ITS HISTORYe 

India rubber or caoutchouc is a very peculiar 
product, Avhicb is found in and extracted from the 
juice of certain trees and shrubs. These are quite 
numerous and are referred for the most part to the 
following families: Euphorbiaceaed, Urticaceaed, Ar- 
tocarpeaed, Asclepiadaceasd, and Cinch onaceaed. It 
is evident that a considerable number of trees nve 
utilized in commerce for its production, and it is 
certain that it exists, quite widely distributed, in 
many cases as a constituent of the juice of plants 
not recognized as containing it. 

When an india rubber tree is tapped, which is 
effected by making incisions in the bark, the sap of 
the tree exudes. It is a milky substance and is 
collected in various ways; it may be in vessels of 



10 EUBBEB HAND STAMP MAKING 

clay^ in shells^ or in other receptacles by the india 
rubber hunters. If this substance is examined it is 
found to be of very remarkable and characteristic 
constitution^ resembling in its physical features 
ordinary milk. It is composed of from fifty to 
ninety per cent, of water^ in which is suspended in 
microscopic globules^ like the cream in milk, the 
desired caoutchouc or india rubber. If the juice is 
left to stand in vessels, like milk in a creamery, the 
globules rise to the surface, and a cream of india 
rubber can be skimmed otf from the surface. If 
the juice is evaporated over a fire, the water escapes 
and the india rubber remains. By dipping an 
article repeatedly in the juice and drying it, a thick 
or thin coating of india rubber can be developed. 
Before the modern methods for the manipulation of 
the gum had been developed, and before the inven- 
tion of vulcanization, this method was adopted for 
the manufacture of shoes. The original ^^ india 
rubbers ^' for protection of the feet in wet weather 
were made in this manner. A clay last was used, 
upon which the india rubber was deposited as 
described. The clay last was then broken out and 
removed. Great quantities of overshoes were thns 
made in South America, and many were exported to 
Europe. 

When caoutchouc has once been removed from 
this watery emulsion, which for all practical pur- 
poses is a solntion, it cannot be restored to the 
former state of liquidity; it remains solid. It will 



AND THE MANIPULATION OF BUBBEli. 11 

absorb a considerable quantity of water^ but will 
not enter again into the quasi solution or combina- 
tion. This property of permanent coagulation, 
which interferes to a degree with its easy manipula- 
tion, was early . discovered. In the last century 
quantities of the natural milk were exported to 
Europe to be used in what may be termed the nat- 
ural process of manufacture, because once solidified 
it could not be redissolved, and because the manu- 
facturers of those days had not the present methods 
of dealing with the apparently intractable gum. 

The natives of South America before the advent 
of Europeans, were familiar with the treatment of 
the juice by evaporation just described and used to 
make bottles, shoes and syringes of it for their own 
use. The name Siphonia applied to several species 
of rubber tree, and seringa (caoutchouc) and 
seringari (caoutchouc gatherer) in Spanish recall 
the old Indian syringes and tubes. 

The gnm is now collected for , export in many 
parts of the world. South and Central America 
are, as they have always been, the greatest produ- 
cers. Some is collected in Africa, Java and India. 
The best comes from Para. However carefully 
treated a great difference is found in the product 
from different countries. The Brazilian india rub- 
ber, known as Para, from" the port of shipment, 
ranks as the best in the market. 

Its history as far as recorded, does not go back of 
the last century. Le Condamine, who explored the 



12 RUBBER HAND STAMP MAKING 

Amazon Rivei% sent from South America in 1736 to 
the histitute de France^ in Paris, the first sample of 
india rubber ever seen in Europe. He accompanied 
the sample with a communication. He said that 
the Indians of that country used the gum in making 
several domestic objects of utility, such as vessels, 
bottles, boots, waterproof clothing, etc. He stated 
that it was attacked and to a certain extent dis- 
solved by warm nut oil. In 1751 and 1768 other 
samples were received through MM. Fresnau and 
Maeqiier, who sent them to the Academy of Sci- 
ences, Paris, from Cayenne in Guiana. 

Although from this period numerous experiments 
were tried with the new substance little of impor- 
tance was done with it for many years. Its first use 
was to rub out pencil marks, whence it derived its 
name of ''^ india rubber/^ As late as 1820 this con- 
tinued to be its principal use. 

An interesting reminiscence of its early history is 
given by Joseph Priestley, the great English chemist 
of the last century, celebrated as the discoverer of 
oxygen. In 1770 he mentioned the use of the gum 
for erasing pencil marks, and speaks of its cost 
being three shillings, about seventy cents, for ^^ a 
cul^ical piece of about half an inch.''^ 

As we have seen, its solubility was early studied. 
In 1761 Herissant added turpentine, ether and 
^^huile de Dippel ^' to the list of solvents. In 1793 
its solubility was utilized in France by Besson, who 
made waterproof cloth. In 1797 Johnson intro- 



ANB THE MANIPULATION OF RUBBER. 13 

duced for the same manufacture a solution in mixed 
turpentine and alcohol. 

The year 18*20 is the beginning of the period of 
its modern use on a more extended scale. Kadier 
developed the methods of cutting it into sheets and 
threads and of wea^dng the latter. Mackintosh in 
1823 began the manufacture of waterproof cloth^ 
using the solution of the gum in coal tar naptha, 
which was caused to deposit by evaporation a layer 
of the gum upon a piece of cloth which was covered 
by a second one. This protected the wearer from 
the gummy and sticky coating of raw india rubber. 
At the best the original Mackintoshes must have 
been very disagreeable articles for wear. 

In 1825 india rubber shoes of raw india rubber 
were imported from South America and formed for 
a while an important article of commerce. 

In 1839 Charles Goodyear, of Massachusetts^ in- 
vented the art of vulcanizing^ or combining india 
rubber with sulphur. It was patented on June 15, 
1844, and covers only the manufacture of soft rub- 
ber. Vulcanite or hard rubber (whalebone rubber) 
is disputed as to its origin, its invention being 
assigned by some to ISTelson Goodyear and by others 
to Austin G. Day, of Connecticut. Good3^ear how- 
ever succeeded in obtaining a patent on May 6, 1851. 
Day obtained a 23atent on August 10, 1858. 

Vulcanization is the most important invention 
ever made in connection with india rubber and may 
fairly rank as one of the greatest discoveries of the 



14 RUBBER HAND STAMP MAKING 

present century. It is claimed by the English, an 
inventor named Handcock being cited as the rival 
of Charles Goodyear. The latter inventor had as 
an associate Nathaniel Hayward^ who is probably 
entitled to some of the credit. 

By vulcanization india rubber loses susceptibility 
ito heat and cold, becomes non-adherent, and insol- 
uble in almost all substances. It is converted from 
a comparatively useless substance into one of wide 
applicability. 

The subject of india rubber is so interesting in its 
theoretical as well as practical bearings that it 
seems impossible that those who are workers in it 
should not feel an interest in its natural history. 
For such readers the chapter on the natural history 
and collection of india rubber has been written. 
As it is a product of widely separated lands on both 
hemispheres, and as it is yielded by an immense 
numbei" of plants, it is impossible in the limits of a 
chapter to give a full outline of its natural history. 

The chapter in question is, therefore, with this 
apology, inserted where it belongs, near the begin- 
ning of the book. Those who are entirely practical 
may pass it over. There is no doubt that the few 
minutes necessary for its perusal will be bestowed 
upon it by some. 



CHAPTER IT. 

THE KATURAL HISTORY AXD COLLECTION OF IXDIA 

RUBBER. 

Africa:n' India rubber is mostly exported from 
the west coast. The belt of country producing it 
extends nearly across the continent. Those who are 
familiar with the India rubber plants of our conser- 
vatories are apt to think of the gum as the product 
of trees, but in Africa it is largely yielded by climb- 
ing plants of very numerous varieties, belonging 
generally to the Landolphia species. It is collected 
by the natives by careless or desultory methods, 
probably less advanced than the ways followed by 
the South Americans. Possibly its -marked inferior- 
ity may be partly attributed to this. It is also sup- 
posed by many that, were the gathering restricted 
to the vine producing the best gum, better results 
would follow. As it is now all gums are mixed 
indiscriminately. African gum is of very inferior 
quality. 

The African India rubber vines grow often in 
dark moist ravines, where no valuable product other 
than themselves could be cultivated. They are 
entirely wild. The vines when cut exude an abun- 



16 BUBBEB HAND STAMP MAKING 

dance of sap^ which differs from the kSoiith Amer- 
ican product in its quickness of coagulation. As it 
escapes from the wound it at once solidifies and pre- 
vents the further escajje of juice. The negroes are 
said to employ the following highly original method 
of collecting it. They make long gashes in the 
bark. As fast as the milky juice comes out they 
wipe it off with their fingers and wipe these in turn 
ou their arms, shoulders^ and body. In this way 
they form a thick covering of inspissated juice or 
caoutchouc over the upper part of their body. 
This from time to time is removed by peeling. It 
is then said to be cut up and boiled in water. This 
is one account. According to others the natives 
remove a large piece of bark, so that the juice runs 
out and is collected in holes in the earth or on 
leaves. Wooden vessels are said to be nsed else- 
where. Sometimes the juice is said to be collected 
upon the arms^ the dried caoutchouc coming off in 
the shape of tubes. A clew to the inferiority of 
African india rubber is afforded by the statement 
that too deep a cut liberates a gum which deterior- 
ates the regular product if it mixes with it. The 
drying of the gum is thought to have much to do 
with its quality and it is highly probable that this 
affects the African product. Some samples seem to 
be partly decomposed they are so highly offensive in 
odor. The South American rubber is often dried 
in thin layers^ one over the other, by a smoky fire, 
which may have an antiseptic effect upon the newly 



AND THE MANIPULATION OF RUBBER, 17 

coagulated caoutchouc. No such process as far as 
known is used in Africa. 

The African india rubber appears under different 
names in commerce. From the Congo region lumps 
of no particular shape called ^' knuckles ^^ ; from 
Sierra Leone smooth lumps; ''negro-heads/'' and 
'^ balls ^' made up of small scrap ; from the Portu- 
guese ports ^^ thimbles/' ^*^ nuts/^ and ''^ negro - 
heads; '" from the gaboon ^' tongues; ^' and from 
Liberia ^^ balls are received. ^^ It is all character- 
ized by great adhesiveness and low elasticitjc 

Prom Assam, Java, Penang, and Eangoon there 
is considerable gum exported. It is supposed to be 
the product of trees of the ficus species, in all these 
places, as it is known to be in Java and Assam. 
In the latter place rigid restrictions are imposed as 
far as possible upon the gathering. In the case of 
wild trees scattered through the forest the carrying 
out of these restrictions is not practicable. The 
trees are cut with knives in long incisions through 
the bark and the juice is collected in holes dug in 
the ground, or often in leaves wrapped up into a 
conical form, somewhat as grocers form their wrap- 
ping paper into cornucopia shape for holding- 
sugar, etc. 

It has seemed reasonably certain that the india 
rubber producing plants might be cultivated with 
profit, and it is as certainly to be feared that 
without such cultivation they will become extinct. 
Efforts have been made in the direction of raising 



18 



BUBBER HAND STAMP MAKING 



them artificially but without much success. In 
Assam numerous experiments have been made to 
propagate the India rubber he-Miwg ficus tree. 

A good instance of the ill effects of carelessness 
in the original gathering of the crop is afforded 
by the Bornese collectors. The source of Borneo 
India rubber is a variety of creepers. These are cut 
down and divided into short sections from a few 
inches to a yard in length. The sap oozes out from 
the ends. To accelerate its escape the pieces are 
sometimes heated at one end. It is coagulated by 
salt water. Sometimes a salt called nijja salt^ ob- 
tained by burning a certain plant {nijjci friiticans), is 
used for the purpose. In either case it is coagulated 




Tree Felled for Collection of India Rubber. 

into rough balls and masses. These masses are 
heavily charged with the salt water^ often contain- 
ing as much as fifty per cent.^ and rarely much less 
than twenty per cent. 

Central America and Panama are great producers 
of the gum. In Panama the custom of felling the 



AND THE MANIPULATION OF BUBBER. 19 

trees is often adopted. In this case grooves are cut 
around the prostrate trunks and under each groove 
as the trunk lies on the ground a vessel is placed to 
collect the sap. Its coagulation is often effected by 
leaving it for a couple of weeks standing at rest in a 
hole, excavated on the surface of the ground, and 
covered over Avith leaves. The caoutchouc sepa- 
rates under these conditions. A quicker method, 
but one yielding an inferior product, is obtained by 
adding to the fresh juice some bruised leaves of a 
plant {ipomcea bona nox) which acts something 
like acid upon milk, in separating the desired solid 
matter or caoutchouc. A jelly like accretion satu- 
rated with blackish water is thus obtained. By 
working it together a blackish liquid is caused to 
escape, and comparatively pure gum is gradually 
obtained. As much as one hundred pounds of 
India rubber may be obtained from a single tree 
where this destructive system is employed. Fur- 
ther north, where a better counsel has prevailed, the 
trees are only tapped, and the India rubber hunter 
is satisfied if from a tree eighteen inches in diam- 
eter he obtains twenty gallons of sap, giving fifty 
pounds of gum. Even where tapping is done the 
tree is often destroyed by carelessness or ignor- 
ance. 

Two systems are followed in Nicaragua. The oper- 
ator ascends by a ladder if he has one, or in any case 
climbs as high as he well can and begins to make a 
longincision. Sometimes he carries one long straight 



20 RUBBER HAND STAMP MAKING 

(nit clear down to the ground. This is made the 
starting point for a number of side cuts, short, and 
running diagonally into it. This is also one of the 
Brazilian methods. The Nicaraguan sometimes 
also makes two spiral incisions, one right-handed 
and the other left-handed, crossing each other as 
they descend so as to divide the surface of the tree 
into roughly outlined diamonds. In either case the 
juice flows down to an iron spout, placed at the 
bottom of the tree, which spout leads to an iron 
pail. The milk is gathered and passed through a 
sieve, and coagulated in barrels by the ipomma plant 
as before mentioned. This gives three grades of 
rubber. The bulk is obtained from the barrels and 
is called oitQwrneros; the small lump which forms in 
the spout is rolled into a ball and called oabezza; 
the dried strips pulled out of the cuts is of very 
good quality and is called bola or huruclia. 

From Brazil is exported the famous Para india 
rubber. This is of very high quality, and is greatly 
esteemed by all manufacturers. No process can 
make a poor gum give a really good product. The 
system of gathering it varies. Sometimes the tree 
is«cut into by gashes from an axe, such gashes ex- 
tending in a row all around the trunk. Under each 
gash a small clay cup is luted fast with some fresh 
mixed clay. These collect from a tablespoonful of 
juice upward, which is collected, and tlie cups are 
removed on the same day. The next day a second 
row of cuts is made below the others, and the same 



ANB THE MANIPULATION OF RUBBER. 21 



process is repeated. This is continued until from a 
point as high as a man can reach^ down to the 
ground the tree is full of cuts. Sometimes a gutter 
of clay is found partly around the trunk with 
gashes above it.- In other cases a vine is secured 




*^^ 



Tree Tapped for India Rubber. 

around the tree and a collecting gutter is worked 
with it for a basis. 

The juice is coagulated rn a smoky fire. A bot- 
tomless jar is placed over the fire and some palm 
nuts are mixed with the fuel. The mould, which is 
often a canoe paddle^ is smeared with clay to pre- 
vent adhesion and is then heated. A cup of juice 
is poured over it, and after the excess has dropped 
off it is moved about rapidly over the smoke and 



22 



BUBBEB HAND STAMP MAKING 



hot air which ascends from the mouth of the jar. 
This series of o23erations is repeated until the coat- 
ing is quite thick; it may be as much as five inches. 
After solidifying over night it is cut open and the 
paddle or mould is removed. After a few days dry- 




Indian Drying and Smoking India Rubber. 

ing it is sent to market. With all the heating, 
during which it sweats profusely, it still retains 
fifteen per cent, of water. 

India rubber sap may be coagulated by an aqueous 
solution of alum. The process has been tried in 
Brazil, and is used to a considerable extent in 



AND THE MANIPULATION OF HUBBEB. 23 

Pernambuco. It was proposed by an investigator 
named Strauss, and the process is still called by his 
,name. One objection is that it gives a very wet 
product, and apparently one of inferior value to the 
smoked gum. 

The feeling that india rubber suffers in the gath- 
ering has been so much felt that it has been re- 
cently suggested that if possible the uncoagulated 
juice should be exported to Europe there to be 
worked up from the beginning. 



CHAPTER III. 

PROPERTIES OF U:N^yULCA2!^IZED AKD VULCANIZED 
li^DIA RUBBER. 

There are two broad divisions to which all varie- 
ties of india rubber can be assigned — unvulcanized 
and vulcanized rubber. Speaking with a certain 
amount of license it may be said that more proper- 
ties characterize the former than the latter. The 
vulcanized article is very slightly affected by ordi- 
nary changes of temperature^ cannot to any consid- 
erable extent be changed by heat short of absolute 
destruction or decomposition^ cannot be united or 
moulded except in simple forms, is highly elastic, 
and is insoluble in almost every solvent for ordinary 
caoutchouc. 

Unvulcanized caoutchouc possesses very interest- 
ing and peculiar properties. The first part of the 
present chapter is devoted to this substance. Those 
who have never seen the crude gum as imported are 
familiar with the article almost pure in the form of 
sheet rubber and black rubber articles generally. 
These are of nearly pure caoutchouc, though recently 
the tendency is to vulcanize them to a considerable 
degree. 



AXD THE MAXIPULATIOX OF BUBBER. 25 

A piece of pure gum containing no combined 
sulphur^ iodine, or other vulcanizing constituent 
will be found to exhibit a very striking peculiaritv. 
Two freshly cut surfaces when placed in contact 
will adhere. This is not in consequence of anv 
viscous or sticky coating. When India rubber is 
cut the surface is perfectly dry and non-adherent 
except to itself. 

The writer once had this property of adhesion 
brought strongly to his attention. In some analyt- 
ical investigations of coal gas he had proposed to 
use finely divided India rubber as an absorbent of 
sulphur. This constituent it absorbs from gas, and 
it seemed that a basis for a quantitative determina- 
tion of sulphur might be found in such propertv. 
Accordingly some raw India rubber was procured 
and with some trouble was cut up into little pieces 
which were put into a bottle. A day or two after- 
wards the pieces united wherever they were in con- 
tact, and an irregular cavernous lump was the 
result. This involved no meltin^r or softeninof or 
change of shape. Each little j^iece was there intact 
and distinct but firmlv attached to its neisrhbors. 

The analogy of this action is seen in lead. Two 
fresh surfaces brought together, preferably with a 
twisting or wrenching pressure, adhere quite firmly. 
The adherence of India rubber and of lead each to 
itself is often exhibited by physical lecturers as an 
illustration of cohesion. The cohesion of india 
rubber is however far more perfect than that of 



26 RUBBER HAND STAMP MAKING 

lead^ probably because of its comparatively great 
resistance to oxidation, and because, owing to its 
elasticity larger areas can be brought in contact. 
Comparatively great though this resistance to oxi- 
dation is, oxygen^ especially in the allotropic modi- 
fication known as ozoiie, may act quite powerfully 
on the gum. Sunlight also can affect it injuri- 
ously. 

A more familiar illustration of the uniting of tw^o 
pieces of the same material is seen in the welding 
of iron. The blacksmith heats two pieces of iron 
until they are nearly white hot and are pasty in 
consistency. On placing them in contact and ham- 
mering to force them together they unite so firmly 
as to be practically one. It is necessary that the 
surfaces of clean metal should be brought together. 
If the pressure induced by the hammering is insuf- 
ficient to bring this about, a flux is added which 
dissolves the oxide and causes the metal to come in 
contact with metal and to weld. The analogy with 
india rubber in its cohesive action is evident. Sur- 
faces long exposed or which are dusty do not cohere. 
The regelation of ice is similar in effect. 

The cohesion of india rubber is important and 
sliould be thoroughly appreciated. It is not saying 
too much to assert that the entire treatment of the 
raw glim depends upon this interesting joroperty. 
The great lumps of gum are torn to pieces and 
washed free from gravel and dirt without going to 
powder, because owing to their elasticity they yield 



AND THE MANIPULATION OF BUB BEE. 27 

and as fast as torn apart the pieces tend to reunite. 
Again india rubber is mixed with pigments and vul- 
canizing reagents by a method practically one of 
grinding or masticating, but the material while it 
changes its shape, and by tlie admixtui'e of the va- 
rious ingredients becomes less strong or easier torn, 
still remains intact, as it welds together or coheres 
as fast as disintegrated. 

As regards its chemical constitution the sap of a 
Para rubber tree has been analyzed with the follow- 
ing general results: (Faraday). 

Caoutchouc 80.70 

Albuminous, extractive, and saline matter, etc 12.93 

Water 56.37 

100.00 

Its specific gravity is 1.012. 

Caoutchouc itself or raw india rubber is a mixture 
of several hydrocarbons of the following composi- 
tion in general: 

Carbon 87.5 

Hydrogen 12.5 

100.0 

Its specific gravity is from .912 to .942. 

The hydrocarbons composing it are isomeric or 
polymeric with turpentine. This fact brings it well 
within the range of familiar vegetable products. 
As will be seen th^ products of its distillation fall 
aniong the same polymers and isomers. 



28 RUBBER HAND STAMP MAKING 

Wlieii pure it is nearly colorless^ the dark color 
being due to impurities. In thin sheets it is almost 
or quite transparent. It burns readily, and with a 
very luminous, smoky flame, as might have been 
anticipated from its composition. The action of 
heat and cold on it is dependent on the degree of 
the temperature. At ordinary temperature it is 
elastic and firm. It can be stretched and will re- 
turn almost to its original size when released from 
tension. Yet the return to its shape is so liable 
to be incomplete, especially after long sustained 
stretching, that pure unvulcanized india rubber is 
considered imperfectly elastic. 

Any elasticity it possesses is principally elasticity 
of shape as distinguished from elasticity of volume. 
In other words when pressed or stretched it may 
change shape to a great extent but hardly change 
its volume at all. A cube of 2}4 inches under a 
weight of 200 tons lost 1-10 of its volume only. 
This is largely due to the fact that it represents an 
approximately solid body, or one destitute of consid- 
erable physical pores. Solids and liquids are very 
slightly compressible. Whatever degree of com- 
pressibility caoutchouc possesses is due principally 
to its minute pores. 

If the temperature is reduced to the freezing- 
point of water a piece of raw jndia rubber becomes 
rigid and stiff. On application of heat it returns to 
its former pliable condition. The same return to 
flexibility may be brought about by stretching it 



AND THE MANIPULATION OF BUBBER. 29 

mechanically. This may be rather a fallacy. 
Stretching india rubber warms it^ so that in this 
mechanically imparted rise of temperature we may 
find at least a probable cause of the softening. 

If the temperature is raised several effects are 
produced, according to circumstances. A piece 
which has been stretched and held stretched, has its 
tension increased by a degree of heat considerably 
less than that of boiling water. Some offer the 
theory that it contains air enclosed in its pores 
which, expanding, produces this effect. As the 
boiling point is reached the material softens and 
becomes somewhat plastic, so that it can be moulded 
into shape to a considerable extent and stretched to 
threads of great fineness. Its elasticity also disap- 
pears as the heat is maintained. These effects in- 
crease in extent up to a heat of 248"" F. (120'' C). 
The return to its original state is not immediate 
however. Some time is required before the reduc- 
tion of temperature will have full effect. 

If now a still higher degree of heat is applied, 
392° F. (200° C.) the india rubber softens to a 
viscous body, or melts. From this state it cannot 
be restored. It remains permanently '* burned ^^ or 
melted whatever is done to it. Some attempt at 
hardening may be made by the use of vulcanizing 
chamicals, but the result will be very imperfect. 

A further increase of heat brings about a destruc- 
tive distillation. India rubber treated in a retort to 
a heat exceeding 400° F. (204° C.) evolves volatile 



30 IWBBER HAND STAMP MAKING 

hydrocarbons of oily consistency, and it distills 
almost completely, a small residue of gummy mat- 
ter or of coke if the final heat has been j^^i^shed far 
enough being left. The distillate is called caout- 
choucin. According to Mr. Greville Williams it con- 
sists of two polymeric hydrocarbons : one, caout- 
chin C10H16, boiling point 340° F. (171° C); the 
other, isoprene CgHg (in formula equal to one-half 
of caoutchin), boiling point 99° F. (37° C). The 
mixture has a strong naptha-like odor and has won 
considerable reputation as being the best solvent for 
india rubber. How far it deserves its reputation is 
a matter open to discussion. 

The solution of india rubber like its fusion is a 
vexed point. There is little question that it can be 
dissolved by proper treatment. Usually naptha, 
carbon disulphide or benzole are used as solvents, the 
choice being guided by motives of cheapness and 
efficiency. 

It is worthy of remark that the formula given for 
caoutchoucin is the same as that of the principal 
constituent of oil of turpentine, and that the latter is 
often recommended as a solvent. Turpentine is 
slightly more volatile than caoutchoucin, its boiling 
point being 322° F. (161° C.) , Other hydrocarbons 
have been recognized in the distillate by Ben- 
ch ardat, Himly and G. Williams, varying in boiling* 
point from 32° F. (0° C.) to 599° F. (315° C), and in 
specific gravity from 0.630 to 0.921. 

Although it has been spoken of as approximately 



AND THE MANIPULATION OF RUBBEB. 31 

solid it does possess microscopic pores, to which its 
limited amount of elasticity of volume is mostly 
due. Thus it is found to absorb water, in which it 
is quite insoluble. As it does this it acts like a dry 
sponge and increases in volume a little, owing to 
dilation of these minute pores. The water absorbed 
may be as much as 18.7 to 26.4 per cent, with an in- 
crease of volume of the gum of xfo-o to jih. When 
it has once absorbed water it is very hard to get rid 
of it. Although the minute surface orifices commu- 
nicate with the entire system of capillary vessels 
and pores, the surface pores on drying contract and 
seal up the absorbed water within the mass. This 
is a clew to the impracticability of the gatherer ship- 
ping dry rubber, and to the great difficulty the 
manufacturer experiences in drying his w^ashed and 
sheeted stock before working it up by masticating* 
or mixing and curing. 

By proper manipulation caoutchouc may be made 
inelastic. This can be done by the freezing process 
or by keeping it stretched for two or three weeks. 
In this way threads can be made to extend and to 
remain extended to seven or eight times their orig- 
inal length. They can then be woven into a fabric. 
On gentle heating their original elasticity reappears 
and they contract. In this way fluted braids can be 
made which will have a high capacity for stretch- 
ing. 

The solution of caoutchouc is difficult often to 
bring about. We have seen that in water it swells 



32 RUBBER HAND STAMP MAKING 

a little without dissolving. In benzole it does the 
same, but swells to a greater extent, to 125 times its 
original volume or even more. Some authorities 
(Watts) go so far as to assert that no solvent com- 
pletely dissolves it. Acting on it repeatedly with 
benzole or other solvent and taking care not to 
break up the swelled mass, from 49 to 60 per cent, 
of soluble matter can be extracted. On evaporation 
this is deposited as a ductile adherent film. The 
swelled up residue which remains undissolved is 
assumed to be the constituent giving strength and 
elasticity, and is only sparingly soluble. If the 
gum is masticated or kneaded at the temperature of 
boiling water a change occurs not well understood, 
by which its solubility is greatly increased. As 
solvents many liquids have been named. Oil of 
turpentine, caoutchoucin, coal-tar, naptha, benzole, 
petroleum-naptha, coal-tar-naptha, anhydrous ether, 
many essential oils, chloroform, bisulphide of car- 
bon, pure, or mixed with seven or eight per cent, of 
alcohol, are among the solvents recommended. A 
mixture of fifty parts of benzole and seventy parts 
of rectified turpentine has been given as a solvent 
for twenty-six parts of the gum. Mastication be- 
fore or after immersion in the solvent is to be 
advised. More will be said on this subject in a 
succeeding chapter. 

Vulcanized india rubber is unaffected by changes 
of temperature within ordinary range. It softens a 
little on heating. Even hard vulcanite when heated 



ANI) THE MANIPULATION OF BUBBER. 83 

can be bent and will retain the bend on cooling. 
It is exceedingly elastic with elasticity of shape bnt 
far less compressible as regards absolute change of 
Yolume than the raw gnm. It melts at 392'' F. 
(200° C.) It cannot be made to cohere, and no 
cement has yet been discovered that will satisfac- 
torily unite two surfaces. It is unaffected by light, 
by ordinary acids and rubber solvents. In contact 
with the latter solvents it swells sometimes to nine 
times its original volume, but on heating returns to 
its original volume and shape. Of water it will 
absorb no more than four per cent, and often much 
less. If it is maintained at a high temperature 
266° to 302° F, (130° to 150° C.) for a long time it 
gradually loses its flexibility, especially if in con- 
tact with metals. Often the escape of sulphuretted 
hydrogen may be observed under these conditions. 
A small admixture of coal tar operates to prevent 
this action. 

Its composition and specific gravity vary widely 
as the most varied mixtures are added by the manu- 
facturer. Its relation of carbon to hydrogen is 
unaffected by the mixtures added. While it may 
contain twenty per cent, or more of sulphur it is 
believed that but a very small quantity is combined 
with it, althougli the excess of sulphur or some 
equivalent, such as sulphide of antimony is essen- 
tial to vulcanization. The combined sulphur is 
from one to two per cent. Some or all of the ex- 
cess of sulphur is mechanically retained, and as the 



34 RUBBER HAND STAMP MAKING 

rubber in ordinary use is worked about^ keeps escap- 
ing and forms a whitish dust upon the surface. By 
treatment with alkali some of the excess of sulphur 
can be removed when the rubber acquires the power 
of absorbing a little more water, up to six and four- 
tenths per cent. 

Boiling oil of turpentine is given as its solvent. 



CHAPTER IV. 

THE MAKUFACTURE OF MASTICATED, MIXEB SHEET, 
AKD VULCANIZED IKDIA RUBBER. 

The manufacture of india rubber relates to the 
production of two principal products. One is mas- 
ticated unvulcanized sheet and thread rubber; the 
other is unmasticated mixed and cured rubber, 
otherwise vulcanized rubber. For the purposes of 
the rubber-stamp maker an intermediate product is 
required, namely, unmasticated mixed sheet which 
is uncured. This is really incompletely vulcanized 
india rubber. 

It will be evident from the description to come 
that it is not advisable for any one -without consider- 
able apparatus to attempt to clean and to wash ('' to 
sheet ^^), to masticate, or to mix india rubber. 
These operations are best accomplished in the fac- 
tories. The partially vulcanized (^^ mixed sheet ^') 
or the pure masticated article are regular articles of 
commerce. Yet a full insight into the manipula- 
tion of india rubber can only be obtained by under- 
standing its treatment from the gum up to the two 
separate lines of products we have indicated. 

A third type of product is coated tissue, such as 



b6 RUBBEH HANB STAMP MAKING 

Mackintosh. This really is a sequence of one of 
the other two processes and a few words will be said 
of it in concluding the chapter. 

As the caoutchouc is received' by the manufac- 
turer it appears an utterly intractable mass. It 
occurs in lumps of every size^ varying in color and 
odor, and very tough but elastic. In virtue how- 
ever of the properties already described, its power of 
cohering when cut, and its softening when heated, 
it becomes amenable to treatment. 

It is to some extent received in such assorted 
condition as to secure even grades, and then each 
grade may be washed by itself. It is thrown into 
water which is in many cases kept at the boiling 
point by steam-heat and left there for some hours. 
It absorbs some water and also softens. Some gum 
is so soft that it will not stand hot water. For such 
the water is kept cold. The purer gum floats; such 
pieces as have stones, dirt, iron, etc. in them, per- 
haps placed there purposely from fraudulent motives, 
sink and can be picked out for separate treatment. 

The lumps are next cut up. A revolving circular 
knife driven by power is often used, and sometimes 
fin ordinary knife is adopted. At this part of the 
operation there is frequently need for sorting, as the 
grades received may have inferior pieces mixed with 
the good. The cutting is mainly to secure good 
grading, and to remove concealed impurities. The 
gum then goes to the w^ashing rollers, called the 
washer and sheeter. fSee cut, p. 37.) 



AND THE MANIPULATION OF RUBBER. 37 

These are heavy corrugated rolls made very shorty 
9-18 inches in length, to prevent springing. They 
are grooved or corrugated and have a screw adjust- 
ment for regulating their distance apart. They 
are geared together so as to Avork in corresponding* 
directions, like a clothes wringer or a rolling mill 
of any kind. The pieces of gum are fed into the 




Washer and Sheeteb,. 

rolls and are drawn between and through them. 
The friction tends to heat the gum. To prevent 
this and also to effect the washing, a supply of 
water, either hot or cold, is kept playing upon the 
mass. This dissolves out all soluble matter and 
washes away mechanically the chips, dirt, etc. 
v/hich may be present. The whole operation is one 
of main force. The caoutchouc is torn and dis- 
tended and delivered as a rough perforated sheet. 
It is passed repeatedly through the machine, the 
rollers being gradually brought closer together, or 
else different sets of rolls are used, set to different 



38 



RUBBER HAND STAMP MAKING 



degrees of fineness. The wash water passes through 
a screen which catches any small detached frag- 
ments of gum. 

Other types of machines have been introduced; 
the above is a representative form. 

The rough sheets must now be perfectly dried, as 
water impairs the final product. This is done in 
drying rooms by steam heat, generally, at a temper- 
ature of about 90° F. (32° C.) The windows, if 
there are any, are painted to exclude sunlight, which 
operates to deteriorate raw gum. When absolutely 
dry the caoutchouc is removed and stacked away 
for use. 



V^VWWV^V^MVttSViWWtBV 




Masticating Machine. 

To prepare pure gum for the manufacture of 
sheet rubber and as a starting point for many other 
preparations; 



the india rubber is ^^ masticated ^^ in 



AND THE MANIPULATION OF RUBBER. 39 

special apparatus. The machine consists of a fixed 
cylinder within which is a corrugated roller set 
eccentrically and rotated by power. The perfectly 
dry sheets in the masticator are pressed and rolled 
and ground and produce a mass of even consistency. 
Here the welding or cohering action again appears 
in its fullest development. The perfect dryness of 
the mass enables it to keep reuniting as fast as 
divided. The action is assisted by the heat gener- 
a^ted, which is not inconsiderable. Sometimes the 
caoutchouc is warmed before introduction, and 
sometimes the roller is heated by 'passing steam 
through it. 




Masticating Machine. 

The masticating machine the French pictur- 
esquely term the wolf (hnp) or devil (diaMe). It is 
given from sixty to one hundred turns a minute, 
and a machine large enough to treat fifty pounds of 



40 RUBBER HAND STAMP MAKING 

gum in a charge^ requires five horse-power to drive 
it. Ill it the sheeted gum is ultimately brought to 
the state of a perfectly homogeneous dark brown 
translucent mass. 

The masticated rubber is peculiarly amenable to 
mechanical and chemical treatment. It can be 
shaped by heat and pressure^ and it is the most 
soluble form and is used for making cement and 
solution^ and is moulded into blocks for the manu- 
facture of sheet and thread rubber. In the process 
neutral body pigments, such as oxide of zinc, or sol- 
uble transparent ones, such as alkanine may be intro- 
duced; easily decomposed matter cannot be incorpo- 
rated on account of the heat. 

In all these machines special provision is made 
to prevent any oil from getting into the gum. 
There is no greater enemy to india rubber than oil 
or fats of any description. The flanges in the mas- 
ticator that roll just inside the bearing are for this 
purpose. 

Sheet rubber is made from the blocks of masti- 
cated gum by slicing. A machine is used for the 
purpose which carries a knife which works back 
and forth in the directioji of its length at high 
speed, making two thousand cuts a minute. The 
knife is kept wet by a stream of water^ and about 
sixty cuts are made per inch. In many articles 
made from this sheet the marks of the cuts can be 
seen as a fine ribbing. The appearance is familiar 
to manv readers. 



ANT) THE MANIPULATION OF RUBBER, 41 

The sheet is often cut from rectangular blocks., 
but cylindrical blocks are also used. The latter are 
rotated in front of the knife edge and a long, con- 
tinuous sheet can thus be obtained. 

The sheet rubber can be cut into threads on web- 
bing and braid. Everyone has noticed that these 
threads are usually square. The method of prepa- 
ration accounts for it. Vulcanized sheet is now 
almost universally used for threads. 

Round threads however can be made by forcing 
softened or partly dissolved gum through a die. 

It is from unvulcanized masticated sheet that 
toy balloons^ tobacco pouches^ etc.^ are made. It is 
the starting point for india rubber bands. For the 
usual form of the latter article the sheet is cemented 
into a long tube which is afterwards cut transversely, 
giving bands of any desired width. To make any 
of these articles satisfactory vulcanization is imper- 
ative. Unvulcanized rubber for many years was 
used, but it is "now completely displaced by the 
vulcanized product. Sheet rubber is made as above; 
is vulcanized by some of the absorption processes 
described in the chapter on vulcaniza*tion. 

We now come to the second product: regularly 
mixed and cured rubber. Its starting point is 
the washed india rubber from the washer and 
sheeter. 

We have seen that the pure gum or caoutchouc is 
very sensitive to changes of temperature. At the 
freezing point of water it is hard and rigid, and at 



42 



BUBBEB HAND STAMP MAKING 



the boiling point is like putty in consistency. 
There are several substances which can be made to 
combine with the gum and which remove from it 
this susceptibility to change of temperature. The 
process of effecting this combination is called vul- 
canization^ and the product is called vulcanized 
india rubber. Sulphur is the agent most generally 
employed. 

In the factory the normal vulcanization is carried 
out in two steps, mixing and curing. The washed 
sheet india rubber which has not been masticated 
and which must be perfectly dry is the starting 




Making Mixed Rubber. 



point, and the mixing rolls shown in the cuts are the 
mechanism for carrying out the first step. These 
are a pair of powerful rollers which are geared so as 
to work like ordinary rolls, except that one revolves 



AND THE MANIPULATION OF RUBBEB. 43 

about three times as fast as the other. They are 
heated by steam, which is introduced inside of 
them. The sheet is first passed through them a 
few times to secure its softness, and then the opera- 
tive begins to sprinkle sul|)hur upon it as it enters 
the rolls. This is continued, the rubber passing and 
repassing until perfect incorporation is secured. 
About ten per cent, of sulphur is added, and a work- 
man can take care of thirty pounds at a time. 

This material is incompletely vulcanized. It is 
in its present condition very amenable to he^t and 
is ready for any moulding jDrocess. Generally it is 
rolled out or ^^ calendered '' into sheets of different 
thickness from which articles are made in moulds 
by curing. 

These sheets are of especial interest to the reader 
as they are the material from which most small arti- 
cles are made, including rubber stamps. 

This rolling of the mixed india rubber into sheets 
of definite thickness is done by special calendering 
rolls. The product is termed ^^ mixed sheet.^^ 

In the mixing rolls the incorporation of other 
material is often brought about. Zinc white, lead 
sulphide, antimony sulphide, chalk, clay, talc, 
barium sulphate, plaster of paris, zinc sulphide, 
lead sulphate, white lead, oxides of lead, magnesia, 
silica, form a list of ordinary mixing ingredients. 
These lower the cost of the finished material and are 
often serious adulterants. For some cases the addi- 
tion if not carried too far is not injurious, or even 



44 



RUBBEU HAND STAMP MAKING 



may be beneficial. A proper admixture renders the 
gum more easily moulded and treated in the shap- 
ing processes. 




Mixing Rolls. 

The next step in the vulcanizing process is the 
heating of the mass^ which step is called '' curing/^ 
Up to a temperature in the neighborhood of that of 
boiling water the mixed rubber can be heated with- 
out change except as it is softened. But if the heat 
is increased it begins to get a little more elastic and 
less doughy, and eventually becomes ^^ cured ^^ or 
vulcanized. The temperature for vulcanization is 
about 284° F. (140° C). The word '' about '' is used 
advisedly, for it is not only a question of heat but of 
time of exposure. After vulcanizing, including the 
curing, India rubber cannot be moulded to any 
great extent. In the manufacturing process, there- 
fore, it is before curing placed in the moulds. 



AND THE MANIPULATION OF BUBBER. 45 

heated, shaped by pressure, and by exposure to a 
higher heat in a steam oven called a vulcanizer, is 
at once cured. 

To prevent adherence to the moulds they are 
dusted over with ground soapstone, and the rubber 
itself is often thus coated. 

The methods of vulcanization and curing, whicli 
may be of special use to the reader, are given in the 
chapters devoted to that sabject (chapter XI.), and 
in the one devoted to rubber stamps. 

Hard rubber, termed ebonite when black, and vul- 
canite when of other colors, is simply vulcanized 
rubber containing a large percentage of sulphur 
added in the mixing process. 

The manufacture of coated tissues is effected in 
several ways. The following is a typical process. 
A mixture of one part washed and sheeted india 
rubber with one part zinc white, one fourth part 
sulphur, and about one third part naptha is mixed 
into a dough-like mass and is spread upon the cloth 
by machinery. The latter is simple. It consists of 
a bare board arranged to move under a scraping bar. 
The cloth is placed on the board and carried under 
the bar. The coating mixture is fed on one side of 
the bar upon the surface of the cloth. As it passes 
under, a regulated amount, according to the set of 
the bar, adheres. It is then dried by steam heat 
and recoated, until ordinarily six coats, eacli about 
one one-hundreth of an inch in thickness, have been 
given. Three coats are given in each direction with 



46 RUBBER HAND STAMP MAKING. 

intermediate drying. The fabric is then cured by 
heat in vulcanizers. 

Sometimes the sulphur is omitted from the mix- 
ture and cold curing, as described later^ is adopted. 
When the goods are made up the seams are secured 
with rubber cement, a thick solution of masticated 
gum. Such seams have to be vulcanized. 

Sometimes two such fabrics before curing or vul- 
canization, are placed face to face and allowed to 
adhere and are then cured or vulcanized. 

Enough has been said in this outline of the man- 
ufacturer's treatment of india rubber to show that 
the first treatment requires machinery. Very little 
can be done with mortar and pestle, although in 
making up solution these simple instrumentalities 
are available. As a starting point for making small 
articles masticated sheet rubber and mixed sheet 
rubber are the staple materials. The preceding 
steps are best accomplished in the factory. 



CHAPTER V. 

IKDIA RUBBER STAMP MAKING. 

We have seen that india rubber cannot be cast in 
moulds. Except in special cases deposition from 
solution is not available. It has to be shaped by a 
combination of heat and pressure. When gently 
heated it softens and can be pressed in a mould. 
As it cools it retains the shape thus given and is 
moulded. This applies to all unvulcanized india 
rubber. If mixed rubber is moulded and heated to 
a higher temperature without removal from the 
mould the curing process is brought about and the 
rubber may be not only moulded but cured and the 
product is moulded vulcanized india rubber. The 
mixed sheet whose manufacture is described in 
chapter IV. (page 42) is the starting point in rub- 
ber stamp making. It is made for this purpose by 
the manufacturers. 

When the material is examined it looks like ordi- 
nary white india rubber, being firm in texture and 
quite strong. On heating to 280° E. to 290<^ E. 
(137° C. to 143° C.) it begins to become ^^ cured/' 
and if in a thin sheet one to ten minutes are suffi- 
cient for the process. As the heat is applied the in- 



48 BUBBEB HAND STAMP ALAKING 

dia rubber first softens and becomes much like putty. 
It can now be pressed tlirough tlie smallest orifice 
and will fill up the finest details of anything it is 
pressed against. It is at this point that pressure 
must be applied to drive it into the interstices of 
the mould. 

As the heat'continues it begins to lose its doughy 
or putty-like consistency. This marks the "reaction 
of the vulcanizing materials. They gradually com- 
bine with and change the nature of the caoutchouc. 
The rubber while still quite soft is elastic. If 
pressed by the point of a knife it yields, but springs 
back to its shape when released from pressure. The 
india rubber is vulcanized. 

On removal from the mould it will be found to 
reproduce its smallest detail. The color and ap- 
pearance have not changed much, but its nature 
and properties are now those of vulcanized rubber. 
It is unaffected by heat or cold within ordinary 
ranges of temperature, and if the india rubber is of 
good quality and made by a proper formula it will 
last for years. 

The tirst thing to be described is the mould, 
which includes the arrangements for pressing the 
sheet of india rubber while heated. A small press 
is needed for this purpose. It may be of the sim- 
plest description, and as an example of a home- 
made but perfectly efficient one the illustration 
may be referred to. The base of the press is a piece 
of iron, if heat is to be directly employed. Where a 



AND THE MANIPULATION OF RUBBEB. 49 

cliamber vulcanizer is used both base and platen 
may be of wood. But from every point of vieAV iron 
is the best. It lasts forever, admits of direct heat- 
ing, and does not split, warp, or char. Through 
two holes drilled near its opposite side§ two or- 
dinary bolts are thrust. It is best to use flat 
headed bolts, and to countersink a recess for the 






Simple Vulcanizing Press for Rubber Stamps. 

heads in order to keep the bottom level. Tlie lieads 
may need to be filed off so as to reduce their thick- 
ness, in order to secure this object. The bolts may 
be soldered in place. 



One thing should be care- 



50 IWBBER HAND STAMP 21 AKING 

fully watched for — the bolts should be set true so as 
to rise vertically from the plane of the base. 

The platen is best made of iron, cut of the shape 
shown. This is an excellent disposition of the 
screw-bolt slots, as by swinging the right end of the 
platen back it can be taken off without removing 
the nuts and lifting it over the ends of the screws. 
Besides the two nnts fitting the thread of the screws 
it is well to have half a dozen extra ones larger than 
the others, which will slip easily over the bolts, so as 
to act as washers. The object of these is to adapt 
the press to objects of different thickness. The 
thread upon an ordinary bolt does not extend clear 
to the head, but by slipping on some loose nuts the 
plates can be forced together if desired. 

This press can be simplified. Both base and 
platen can be made of wood, the platen being sim- 
ply bored for the bolts, and the latter driven tightly 
through the holes in the base so as to retain their 
place. Even this can be improved on as regards 
simplicity. Two blocks of wood screwed together 
by two or more long wood screws may be made to do 
efficient work. 

' One trouble is apparent with all these devices, 
and that is the want of parallelism of the opposed 
planes. The base and platen may .be true and 
parallel or they may not. Perhaps the simplest 
way of securing this is the best. It consists in 
placing across the base two distance pieces, which 
may be slips of wood. These must have perfectly 



AND THE MANIPULATION OF BUB BEE, 51 

parallel faces. As the press is screwed up they will 
be gripped between the platen and base and will 
not only ensnre their parallelism but will keep them 
at an exact distance apart. Such distance pieces 
are shown in the same cut. Pieces of printers^ 
^^ furniture/^ spaceS;, or ^^quads/^ may be used for 
this purpose. They should not be fastened in place 
if there is need to adapt the press to more than one 
thickness of material and matrix. 

The above described apparatus is a vulcanizing 
press. A further improvement in it may be effected 
by the use of spring pressure. Two strong spiral 
springs may be dropped over the bolts^ the nuts 
being screwed on above them^ or a powerful spring 
of flat brass or steel ribband bent into the shape of 
a shallow letter V may intervene between nats and 
platen^ the centre of the bend bearing against the 
centre of the platen. 

As regards the strength of the springs there is 
this to be said. The distance pieces will prevent a 
spring that would ordinarily be too powerful from 
doing any harm. Such distance pieces should be 
used, as the springs must be based upon giving a 
pressure of many pounds per square iuch of surface 
to be acted on. They should have a range of an 
eighth of an inch or more. The greater the range 
the more evenly will they work. 

The next cut shows an excellent little screw press, 
that is made for the purpose of pressing vulcanizing 
flasks. This is so simple that it will suggest to the 



C)2 liUBBEli HAND STAMP MAKING 

mecliHiiical reader how lie can make a single-screw 
press^ which is by far the most convenient. to use. 
In the stationery stores very small model cast iron 
copying presses designed for use as paper weights 
are sold. They are excellent for a limited amount 
of small sized work. 




Vulcanizing Flask Clarip. 

A large sized gas heated press, such as made for 
the purpose of manufacturing rubber stamps^ is 
shown in the next cut, p. 53. Its construction is 
obvious. It is termed by the trade a vulcanizer. Its 
manipulation will be given further on. 
' Type are generally the object to be copied. 
These are best set up with high quads and spaces. 
Naturally rather a large type is chosen, with extra 
Avide spaces between the letters. Some advise rub- 
bing the type faces full of hard soap, afterwards 
brushing off the face, leaving the hollows filled. 
Sometimes wax is recommended for the same pur- 



AND THE MANIPULATION OF RUBBER. 53 

pose. This prevents the plaster of the matrix en- 
tering so deeply into the cavities of the letters. 

The type forming the model to be reproduced, is 
locked in a frame. Two pieces of printers' furni- 




Gas-heated Stamp Vulcanizer. 

ture or other wooden strips screwed together by 
wood screws at their ends will answer for a locking- 
frame for small inscriptions. 

The model to be copied need not be type, but any 
desired relief may be used, such as an electrotype, a 
stereotype, an engraving or another rubber stamp. 
In any case it is to be placed upon a flat surface, 
best an ''^imposing stone"' or piece of marble, witli 



54 liUBBEIl HAND STAMP MAKING 

the inscription nj^vvards. On each side of it dis- 
tance pieces reaching about one-eighth inch above 
its upper surface are to be placed. 

The next shaping appliance is the matrix or 
mould, or reverse of the model which is to be 
copied. This in the case of rubber stamps is prop= 
erly called the matrix. Those who have witnessed 
the stereotyping of a large daily newspaper have 
seen the matrices of the tyj)e made of paper and 
paste, the whole mixture being termed ^^ flong.^'' 
Such a matrix is required for rubber type, but 
paper is rather too susceptible to heat although good 
work can be done with it. It also does not enter as 
deeply into the cavities of the type as is desirable. 
As a rule a fine quality of plaster of paris is to be 
recommended. What is sold as dental plaster is 
the best, but common plaster can be used. It is 
mixed with water or with a solution of gum arable 
or dextrine in water. For the latter enough gum 
should be added to make the mixing solution as 
thick as thin syrup. 

A piece of iron, perfectly flat and true, is now to 
be taken, large enough to more than cover the 
inscription to be copied. Upon its surface a putty 
m'ade of the plaster and the liquid used in mixing 
is to be spread. This should be rather stiff. The 
surface of the iron should not be too smooth as it is 
desirable that the plaster should adhere well on 
setting. The plaster should be smoothly spread to 
a depth of three-sixteenths or a quarter of an inch. 



AND THE MANIPULATION OF RUBBEE, 55 

It is best applied with a palette knife or trowel, 
although a table knife will answer perfectly. If its 
surface does not become smooth it can be made so 
by applying a little of the solution with the knife 
or trowel. 

Before this has been done the model must be 
oiled. Olive oil or other clear oil is applied to all 
parts of the type faces, and the excess is then wiped 
olf and cleared out of the interstices with a piece of 
blotting pai3er. 

Xext the plate with the plaster is inverted and is 
pressed steadily down upon the model until it 
strikes the distance pieces. It is left to set. In 
about ten minutes it can be raised, wdien it will be 
found to give a beautiful impression true to the 
smallest detail of each letter. 

It has been said that water may be used as the 
mixing fluid. If this is done it is well to strengthen 
the mould by saturating it with an alcoholic solu- 
tion of shellac, after it has dried thoroughly, best 
for a few hours in an oven. This operates to 
strengthen the small projections that are liable to 
crumble or to break olf in use. 

The dealers in rubber stamp supplies sell a lever 
j)ress for conducting the operation of producing the 
matrix. The type is locked in a special chase, 
which is carried on a bed that travels under and out 
from under the platen of the press upon rollers. 
From each corner of the chase in which the type 
model is locked, a pin rises which is encircled by a 



56 liUBBEH HAND STAMP MAKING 

spiral spring. A square frame of flat iron with 
lioles at the corners for the pins to pass through, 
rests upon tliese springs well above the type. 
The pins pass through holes in its corners. The 
matrix plate with its coating of plaster is placed 
upon this frame, which supports it above and not 
touching the type. The whole is now rolled under 
the press and the lever pulled to produce the im- 
pression. As the pressure is released the frame 
with the matrix is raised from the type by the 
action of the springs. This can be done immedi- 
ately, and before the plaster has set. It is almost 
impossible to raise it by hand with the requisite 
steadiness. The same chase wdth corner pins and 
springs can be used in a screw press, the one press 
answering for making the matrix and for moulding 
and curing the stamps. The plaster matrix can 
also be made by casting from a thinner mixture of 
plaster and water. After the type has been set up, 
or the model has been selected and placed face up 
and horizontal, a little ridge or projection must be 
made all around it. Paper can be pasted around it, 
and w^ound with thread for this i^i^^i'pose. It is 
oiJed and wiped off as before. The plaster is now 
mixed with water to the consistency of cream, and 
is poured upon the model until it lies even with the 
projecting ledges or paper border. In an hour or 
less it can be removed. If water is used the mould 
should before use be treated with shellac solution as 
already described. The plaster may also be mixed 



AND THE MANIPULATION OF BUBBEB. 57 

with gum arabic solution, or with three to ten per 
cent.' of powdered marshmallow root. This in- 
creases its toughness. 

What is known as the oxychloride of zinc cement 
•appears to the author to be far. preferable to com- 
mon plaster of paris. It is a trifle more expensive, 
but it costs so little that it is well worth trying.' It 
is made by mixing oxide of zinc with a solution of 
zinc chloride. Xo particular strength of solution 
or proportions are prescribed; the zinc chloride solu- 
tion should be a strong one^ and the mixture should 
be of about the consistency of soft putty. 

Zinc chloride may be bought as a solid substance 
or in strong solution. The latter answers for the 
mixing directly. It may also be simply made by 
dissolving metallic zinc in strong hydrochloric acid. 
The manipulation is exactly the same as with 
plaster of paris. 

The manufacture of papier mache and of other 
matrices is given in a special chapt-er. For all ordi- 
nary purposes the plaster or cement matrices are 
ample. 

The stamp is made from the mixed uncured sheet 
rubber, wliose preparation in the factory, including 
the operation of calendering it into sheets, has 
already been described. The best advice the reader 
can be given is not to attempt to make it except as 
a matter of interest and experiment. It can be 
purchased especially prepared for stamps from the 
dealers in india rubber. 



58 liUBBEB HANI} STAMP MA KIN a 

A piece is cut from the sheet large enough to 
cover the face of the matrix. It should have a 
perfectly smooth surface, without cloth wrapper 
marks sometimes found impressed on it. The sheet 
as received from the maker is about one-eighth of an 
inch thick. It is thrown into a box of powdered 
soapstone or talc to secure a coating of the same on 
both sides. A little is dusted over the matrix and 
the excess is blown off. The matrix is now jolaced 
upon the base of the press, and heat is appliedo 

To carry out the process most simply the press if 
of metal may be placed upon a support over a gas 
burner or kerosene lamj), or even on a kitchen range 
or stove. It will in a few minutes become warm. 
The sheet of india rubber is now dusted off and is 
placed in the press upon the matrix. The platen of 
the press is screwed down upon it. 

As the india rubber becomes hot it begins to 
soften and flow. By the action of the screw of the 
press it must be forced down from time to time as 
it softens. This drives the putty-like material into 
all the interstices of the mould. The excess escapes 
from the sides of the tympan in cases where the 
latter is of restricted area. The press theoretically 
should be heated to the vulcanizing temperature, 
which is 284° F. (140^ C). In practice the heat is 
not determined with a thermometer. Tlie operator 
learns by experience how much heat to apply. The 
regulation type of gas heated press or stamp vulcan- 
izer is shown in the illustration on page 53. 



AND THE MANIPULATION OF BUBBEE. 59 

As some of the India rubber is sure to protrude^ 
the progress of the work can be watched from its 
action. By pressing the point of a knife against it 
the period of vulcanization can be told. Before 
the material is .heated it is elastic and resists the 




Oil Stove for Heatikg Vulcanizers. 

pressure of the knife; as heat is applied it becomes 
soft like putty; as the heat increases it again stiffens 
and becomes quite elastic. At this point the press 
can be opened and the sheet and matrix can be 
taken out or the platen swung aside. On pnlling 
or stripping the sheet from the matrix it will be 
found to reproduce the model in elastic india rubber 
to the minutest detail. 

As regards the minor details there is something 



60 RUBBER HAND STAMP MAKING 

to be said. Distance pieces to gauge the thickness 
liave been recommended" for the home-made press, 
page 48. Care must be taken to have these low 
enough to provide for enough excess of material to 
produce a good impression. For ordinary stamp 
work they should allow about one-sixteenth of an 
inch for the '* squeeze. "" It will be seen tliat by using 
the distance or gauge pieces both for making the 
matrix and for moulding and curing the stamp, abso- 
lute parallelism of surfaces will be secured. 

The reader will have noticed in the description 
and will find at once in practice that the press has 
to be screwed up as the rubber softens. Where 
heavy iron presses are used the large mass of heated 
iron comprised in the platen of the press instantly 
heats the upper surface of the india rubber sheet and 
tlie heat immediately penetrates into it, while the 
heated matrix heats it from below. Thus it softens 
at once, and the press is directly turned down and 
the india rubber is driven into the mould and curing 
at once begins. But where small presses are used 
this manipulation is not so easy. For such the 
springs mentioned on page 51, are highly to be 
recommended. The matrix and india rubber can 
be put into the cold press, and the tympan with 
intervening springs can be screwed down so as to 
compress them. Then on .applying heat the mould- 
ing takes place automatically. 

With a hot press and good sheet a period of three 
to ten minutes is ample for moulding and curing. 



AND THE MAN IP ULA TlOX OF li UB BEB, 6 1 

Instead of sprinkling with talc the matrix may be 
oiled and sprinkled with plumbago and afterwards 
polished with a brush. This is not so clean a ma- 
terial as talc and is not to be recommended for 
general use, especially as oil is a bad substance to 
bring in contact with rubber. 

Tiie distance or gauge pieces whose use has been 
recommended are not necessary where presses work- 
ing truly parallel as regards their opposing faces are 
used. But where home-made apparatus is used 
they will be found a valuable addition. 

In describing the simple press it was said that it 
could be made of wood. It is evident that a wooden 
press could not be used for direct heating. Such a 
press must be used in a hot chamber or vulcanizer^ 
properly so called. Originally rubber stamj^s were 
generally made in chamber vulcanizers. 

The next cut shows a combined matrix making, 
moulding and vulcanizing apparatus of very conven- 
ient and compact form and adapted for rapid work. 
As the press stands in the cut the matrix ]3ress is 
seen in front. A box or chase is carried under its 
platen by two trunnions, so as to be free to oscillate 
to a limited extent^ The type model is secured in 
this box. Above this box or chase is a cross-bar 
with screw and platen attached, connected at will to 
two standards or pillars, so as to constitute the 
matrix press. 

A matrix plate swings on a hinge joint between 
the two presses. The hinge-pin is removable. Its 



62 



RUBBER HAND STAMP MAKING 



ends can be seen projecting to right and left of the 
press columns. The hinge is at such a height that 
when the matrix plate is swung forward over the 
type box it will rest upon it in a nearly horizontal 
position. The pivoted box will adjust itself so as 
to come into parallelism with the plate. 




Matrix Making, Moulding and Vulcanizing Apparatus. 

"When the matrix plate is swung back it falls 
upon the base plate of the vulcanizing press seen in 
the rear. 

In use the composition used for the matrix is 
spread upon the matrix plate, which may for this 



AND THE MANIPULATION OF RUBBER. 63 

purpose be removed from the apparatus. It is 
replaced and the hinge-pin is pushed home. This 
is done with the composition coated side facing the 
front of the apparatus as it stands in the cut. The 
plate is then swung forwards^ the platen of the 
matrix press being turned forward out of the way, and 
is pressed down upon the type or other model that 
rests in the type box. If desired the press is used 
to force it home. The cross-bars of both the presses 
are arranged to swing each one on one of the 
pillars, so that the platens are turned to one side out 
of the way of the matrix plate as it is swung back 
and forth. 

The pressure is released and the platens are 
turned aside. The matrix plate is swung over to 
the rear upon the bed-plate of the vulcanizing 
press. Here it lies with the com230sition=matrix 
upwards. 

A lighted lamp, either alcohol or gas, is placed 
beneath the bed-plate of the vulcanizing press on 
which the matrix rests. This quickly dries it and 
brings it to a good curing temperature. The cross- 
bar and platen may be swung over it during the 
heating so as to be heated at the same time. The 
matrix is talced when dry and hot; the mixed sheet 
itself talced, is placed upon the matrix, the platen 
is screwed down upon it, and in a minute or two 
the moulding and curing is completed. 

A vulcanizer, properly speaking, is a vessel ar- 
ranged to heat to a definite degree any desired arti- 



64 RUBBER HAND STAMP MAKING 



Rubber Stamp Vulcanizer. 



cles which are to be cured. The favorite type have 
been the steam vulcanizers. If steam is generated 
from water at a constant pressure, otlier things 



AND THE MANIPULATION OF liUBBEB. 66 

being equal a constant temperature will be pro- 
duced. By raising or lowering the pressure the 
temperature can be made to rise or fall. A steam 
vulcanizer is a tightly sealed vessel which contains 
water and which is provided with a thermometer or 
a pressure gauge as well as a safety-valve, safety 
disc or safety plug. By keeping the gauge at con- 
stant pressure or by keeping the thermometer con- 
stant the temperature can be limited and kept 
steady. The following table gives some pressure in 
pounds per square inch with temperatures corre- 
sponding to steam of such pressures: 



;. per square 


inch. 


Temp. Fahr. 


Temp. Cent. 


45.512 




275° 


135° 


52.548 




284° 


140° 


60.442 




293° 


145° 


67.408 




300.2° 


149° 



The illustration, p. 64, shows a vulcanizer of modern 
type made for rubber stamp work. In some recent 
vulcanizers the water and steam are excluded from 
the vulcanizing chamber, being contained within 
double walls forming a steam jacket and maintain- 
ing a constant heat within the chamber. These 
illustrate a point that has been much misappre- 
hended, namely that curing is independent of pres- 
sure or atmosphere. Because vulcanizers have 
generally been filled with steam at high pressure 
many have supposed that the steam or pressure had 
something to do with their action. The fact is that 



66 RUBBER HAND STAMP MAKING 

it is only the heat due to the steam at such pressure 
that is instrumental. Steam is a very powerful 
radiator and absorber of so called radiant heat. For 
this reason an atmosphere of steam maintains all 



Steam Jacket Vxtlcanizer. 

parts of the vulcanizer at an even temperature and 
is to that extent advantageous. Its presence and 
the pressure it generates are not by any means re- 
quired for vulcanizing. Its pressure is entinely 
without effect. 

To use a steam vulcanizer^ water is introduced. 



AND TEE MANIPULATION OF BUBBER. 67 

the article in the press or mould is placed in it^ and 
the top is secured. Heat is then applied^ best if on 
the small scale, from a Bunsen gas burner gas, or oil 
stove. Either the pressure gauge or thermometer 
may be watched> and the flame turned up or down 
to keep it at the proper temperature. 

Moulding cannot be executed in the ordinary 
closed chambers. The press must first be heated to 
the temperature of boiling water or thereabouts and 
the moulding is then effected by screwing down the 
mould screw, upon the sheet and matrix. It is 
then placed in the vulcanizer and cured. 

The manufacturers supply gas regulators which 
automatically regulate the gas supply. These are 
worked by the steam pressure. If any one wishes 
to study the practical manipulation of small steam 
vulcanizers he can see them in use at any dentist^s 
office. 

There is no need of a steam vulcanizer for ordi- 
nary stamp work. The hot press system already de- 
scribed answers every purpose and is in use by the 
most advanced manufacturers for thin sheet work. 
But if a wooden moulding press is used then it must 
be heated in a vulcanizer or some kind of oven or 
hot chamber. 

A very simple and reasonably satisfactory oven or 
air bath can be made from a flower pot and a couple 
of tin plates. A plate larger in diameter than the 
mouth of the flower pot forms the base of the ap- 
paratus. This is supported on a stand over the gas. 



68 



BUB BEE HAND STAMP MAKING 



lamp or other source of heat. A smokeless flame or 
one depositing no lampblack should be used. Alco- 
hol or a kerosene oil stove illustrated on page 59 are 
excellent. On this plate a smaller plate is inverted, 
which latter must be so small as to be surrounded 
by the flower pot and to be included within it when 
the pot is placed over it like an extinguisher. 




Flower Pot Vulcanizer on Stand. 

A chemical or round stemmed thermometer is 
arranged to go through the aperture in the up- 
turned bottom of the pot. This may be hung from 
a support or it may be secured by passing through 
a hole in a cork or block of wood. Its bulb should 



AND THE MANIPULATION OF BVBBER. 69 

be near the part of the chamber to be occupied by 
the mould or press. 

The press with the article to be cured is placed 
upon the inner plate. The temperature is main- 
tained at the proper point by regulating the heat, 
and all the conditions for excellent work are sup- 
plied. The disposition of the apparatus is shown in 
the cuts. 




Interior of Flower Pot Vulcaxizer. 

Another arrangement equally simple is given in 
the next cut. An iron kettle has a layer of type 
metal or lead poured an inch thick cast within it 
upon its bottom. A thermometer passing through 
a hole in the cover enters a cup of glycerine that 
stands upon the bottom. This gives the tempera- 
ture. 

The object of having a thick or a double bottom 
is to prevent excessive radiation of heat from any 
one part. The essential condition for good opera- 



70 BUB BEE HAND STAMP MAKING 

tion is to maintain an even temperature throughout 
the chamber. 




Fish Kettle Vulcanizer. 

The thermometer is not an absolute necessity. 
By removing the press from time to time and in- 
specting the overflow of india rubber the progress 
of the operation can be watched. An extra piece 
of india rubber may be placed on a piece of wood 
by the side of or upon the wooden portion of the 
press, and its condition can be taken as the crite- 
rion. Pressure with the point of a. knife will tell 
the vulcanizing point. 

By the press system of curing, a heat far above 
the vulcanizing temperature may be made to do 
good work by a very short application. There is 



AND THE MANIPULATION OF BUB BEE. 71 

however danger of burning the work if left in too 
long. If the air-bath with thermometer or the 
steam vulcanizer is used, and the heat is kept down 
to the proper curing temperature, there is no danger 
of burning the india rubber even if the curing is 
considerably prolonged. 

As the flower pot has often to be lifted off for 
introduction or removal of the press, and as it gets 
quite hot, a holder of some kind is requisite. A 
piece of heavy blotting paper is very convenient for 
this purpose. 

The flower pot system with thermometer can be 
further simplified by being used on a stove or range. 
A china saucer inverted, or some similar support, 
should be placed under the pot. A part of the 
stove at very low heat will suffice. The kettle vul- 
canizer, can also be placed on a stove so as to dis- 
pense with gas or oil. 

Finally^ as the last step in simplifying the work,. a 
stamp can be made without any special apparatus 
beyond a hot flat iron. The matrix may be placed 
on a stove where the heat is rather low, the talc- 
coated mixed rubber siieet placed upon it, and on 
this a hot flat iron. In a few minutes if the heat is 
sufficient the stamp will be finished. 

A few words may be said about the type. High 
spaces and quads between the letters should be used, 
such as will come up to the shoulder of the type, as 
has been said. But a very nice effect is produced 
by using low quads between words. This leaves 



72 RUBBER HAND STAMP MAKING, 

each word elevated by itself, producing a good 
appearance. 

. Autograph stamps are made from a model cut in 
Avood by a wood engraver. The autograph is writ- 
ten in some form of copying ink upon a piece of 
paper, and is transferred by moistening and, pres- 
sure to a block of wood. With an engraver^s tool 
the wood is cut away from the lines, as the block is 
routed after the inscription has been ^'^ outlined. ^^ 
The woodcut is used as a model for making a 
matrix. 

It is evident that an autograph of fair quality 
could be obtained from a chalk plate. But in rub- 
ber stamp work to get good results certain essential 
parts should be of the best. These parts include 
the mixed rubber, model and matrix. A departure 
from excellence in any of these tends to the produc- 
tion of an inferior stamp. What is known as a 
'^healthy cure^^ is above all essential to the appear- 
ance of the product. 

The stamp thus made is attached to a wooden 
handle by common glue or by one of the rubber 
cements given in chapter XVI. 



CHAPTEE VI. 

INDIA RUBBER TYPE MAKII^O. 

India rubber tyj)e are often used to set up differ- 
ent inscriptions in wooden handles^ or different date 
figures in rubber stamps. The latter are in such 
cases made with slots or recesses to receive them. 
Rubber type are much shorter than regular type^ 
and as a rule are larger in the body in proportion to 
the face- of the letter. Where only a few^ are re- 
quired the following process is the simplest way of 
making them from mixed rubber sheet. 

The type wdiich are to be copied are set up on a 
level base or imposing stone^ and quads or spaces 
are put between them. High quads and spaces 
should be used; otherwise they should be pushed np 
until even with the shoulders of the type. After 
oiling the faces a matrix is produced exactly as 
described for stamps. Before it has set quite hard 
the plaster or cement is cut off so that it will just fit 
within a little ^^ flask ^^ or frame. 

The latter may be made of tin or wood and may 
be rectangular or circular^ provided it is large 
enough to include Avithin its area the full working 
face of the matrix. It should be about half an inch 



74 



RUBBER HAND STAMP MAKING 



or five-eiglitlis of an inch deep. Its object is to pre- 
vent the softened india rubber from spreading, so 
as to secure the requisite height of the type pro- 
duced. 

A piece of wood or metal is cut so as to fit closely 
within this frame like a plunger. It is provided 
with shoulders or cross pieces, so as to limit the 
depth to which it can be inserted. It will be seen 
that when matrix, flask, and plunger are all put 
together a complete mould for a block of type is 



c 


1 


1 


i 


1 








f — 


1 


— p 



India Rubber Type Mould. 

produced, as shown in the illustration, the matrix 
with its plate forming the bottom of the box. 
After the flask is placed upon the matrix it is filled 
with the mixed uncured india rubber sheet. As a 
matter of preference thick sheet is used, but scraps 
of all shapes can be employed as it all fuses to- 
gether. The mould and matrix are of course first 
well dusted with talc powder. The plunger is put 
on and the whole is pressed. Heat is next applied 
in a vulcanizer or hot air chamber, such as the 
flower pot arrangement, or in boiling water. As the 
sheet reaches the boiling point 212° F. (100° C.) the 
flask is removed and the plunger examined. If it 



AND THE MANIPULATION OF RUBBER. 75 

goes down to its seat without expelling any india 
rubber more of the latter is required and is accord- 
ingly inserted, the plunger being taken off for the 
purpose. The softened gum should ooze out around 
the sides of the plunger. The whole is again put 
under pressure, and the platen is screwed down, and 
if all is right an excess of rubber showing itself, the 
whole is put in the hot chamber, the heat is raised 
to 284° F. (140° C), and is maintained there for 
half an hour. 

It is almost a necessity to secure the matrix j^late 
to the bottom of the flask. This for a single opera- 
tion may be done by screws, or lor several operations 
by hooks or catches. 

When the curing is complete the mould is re- 
moved from the vulcanizer, is allowed to cool and is 
opened. The block of type will come out with per- 
fect reproduction of the letters upon one side. If 
all the directions have been followed as regards dis- 
tance pieces, level imposing surface, etc., both faces 
will be exactly parallel, and any number of other 
blocks can be reproduced of exactly the same 
height, not necessarily from the same matrix, 
although one good matrix can be used many times. 

The type have now to be cut apart. This is done 
with a sharp knife which is kept wet. It is worked 
with a saw^ing motion, and if sharp and properly 
used will cut with regularity, and smoothly. Type 
with knife marks on the sides are always unmechan- 
ical in appearance and seem to be ^Hiome made.^' 



76 RUBBER HAND STAMP MAKING. 

The object of using higli quads and spaces or of 
pushing them up, will now be evident. It secures 
the evenness of the general face of the block of 
letters^ which otlierwise would have a deep depres- 
sion between each pair of letters. If the quads and 
leads are properly arranged, the letters will project 
upwards from a smooth, plane surface. 

The dealers in rubber stamp maker^s supplies sell 
special steel moulds for the purpose of making 
them. This does away with all necessity for making 
matrices, and making up a flask, etc. The general 
manipulation is that given above. Where many are 
to be made the regular mould is by all means to be 
recommended. 

Sometimes type are made by cementing single 
letters made by the stamp process upon wooden 
bodies. 



CHAPTER VII. 

THE MAKI]S"G OF STAMPS AIS^D TYPE FEOM YULCA:N^- 
IZED li^DIA RUBBER. 

Although all reference hitherto in the matters of 
stamps and type has been to their manufacture from 
uncured india rubber, a good deal can be done with 
vulcanized and cured gum. The stock that is 
known in the trade as pure gum, such as is used for 
bicycle tyres, for steam packing and the like, can 
be made to yield to moulding to a certain degree. 
It will not flow and unite as will the uncured gum, 
but it is evident that in certain cases its stiffness is 
even an advantage. Thus with it, rubber type can 
be made without any flask or frame. The material 
has stiffness enough to support itself. 

The manipulation is of the simplest. A piece is 
cut out with a knife so as to be of proper thickness 
and size. It should be a little thicker than will 
ultimately be required. The two opposite surfaces 
should be smooth and parallel. It is talced, and 
placed in the press with the matrix beneath it, and 
subjected to pressure by the screws being turned 
down. It is then placed in the vulcanizing 
chamber and heated to about 284^ F. (140° C). 



78 RUBBER HAND STAMP MAKING 

After it has become hot it softens a little. The 
press is removed from the hot chamber and is again 
screwed down as hard as the matrix can stand. 
This point is largely a matter of judgment. The 
heat is largely indifferent as long as it is anywhere 
near the above temperature. 

By one or two repetitions of the pressing and 
heating the softened India rubber can be made to 
take quite a deep impression from a suitable matrix. 
It is allowed to cool under full pressure. When 
removed from the press^ it will retain the characters. 

It is evident that impressions in as high relief or 
as deep and clear as those yielded by nncured india 
rubber need not be expected. But where the other 
cannot be had^ or where some experimental or tem- 
porary work only is on hand^ this process will be 
very convenient. 

The material may be half an inch thick. Prom 
such india rubber type can be cut with advantage. 

Old rubber can be thus used. The writer has ob- 
tained excellent results from pieces of an old dis- 
carded bicycle tyre. 

The great point is to apply a heavy pressure to 
the hot material. Many other articles can be thus 
produced extemporaneously. At the same time it 
must be considered only a makeshift. . One who has 
used the soft^ easy flowing uncured gum would 
never be reconciled to the use of so rigid and diffi- 
cultly moulded a material^ one too that can never 
be trusted to reproduce intricate moulds of consid- 



AND THE MANIPULATION OF RUBBER, 79 

erable depth. In the slow yielding of the half 
melted uncuredgum, so amenable to slight pressure^ 
a quality of availability is found that is missed in 
the other. One is worked by main force where the 
other readily yields and takes the most complicated 
shapes. 

By the above process stamps of such thickness 
may be made that they cun be nsed without handles. 
It is also useful for impressing a designation of any 
kind upon ready cured articles. It suggests a very 
useful department of manipulation of India rubber. 

The heating and moulding can be done also in a 
hot liquid bath such as described in chapter XI. 



CHAPTEE VIII. 

VAKIOUS TYPE MATRICES FOR RUBBER STAMPS A:N'D 

TYPES. 

Matrices for stamp moulds can be made by sev- 
eral of the methods used by stereotypers. Thus an 
electrotype could be taken directly from the face of 
the type. There would be little or no utility in 
doing this where the simpler processes are available. 

PAPIER MACHE MATRICES. 

The stereotyper for daily newspaper work uses 
very generally the papier mache or " flong^^ process 
of reproducing the page. This is also available for 
rubber stamp making. 

The first requirement is paste. This is made by 
softening twelve parts of whiting in forty parts of 
water^ letting it soak for an hour or more. Nine 
parts of wheat flour are added. This is best mixed 
with a little water before adding to the main mix- 
ture. It is then brought to the boil and seven parts 
of glue softened by soaking in twenty-one parts of 
water, are added. For each gallon of such mixture, 
one ounce of white crystallized carbolic acid is 
added if it is to be kept for a long time. 



AND THE MANIPULATION OF BUBBER. 81 

The '^ flong ^' is made by pasting together^ one 
on top of the other, a sheet of fine hard tissue 
paper, three sheets of blotting paper (about 23 
pounds to the ream), and a heavy sheet of manilla 
paper. The pasting must be smooth and eacli 
layer must be pressed and rubbed down, but not too 
hard. It is very important to secure perfect 
smoothness and regularity, and entire absence of 
air bubbles. 

Every printing office where the process is used 
has its own traditions as to the preparation of flong. 
As a great deal depends on manij)uiation, it would 
be well to endeavor to inspect its practical use in a 
newspaper printing office before making it. Eeady 
prepared flong can also be procured. 

The form of type must be very clean and there 
must be no paste on the tissue paper face of the 
flong. The type are lightly oiled, some powdered 
talc is dusted over the damp tis-sue paper face of 
the flong, and the mass is laid face downward on 
the type. With a stiff haired brush the paper is 
now beaten down against the type. Great care 
must be taken to beat vertically; a slight side action 
will ruin the resulting matrix. If the brown paper 
will not stand the beating, a cloth may be spread 
over it. 

The progress of the work can be watched by rais- 
ing up a corner from time to time. When suffi- 
ciently deep the last touch is given by the printer's 
planer. This is a block of hard wood. It is placed 



82 RUBBER HAND STAMP MAKING 

upon the back of the floiig and is hammered down. 
The operation is repeated until the entire area, has 
been treated. For much rubber stamp work the 
area wouhl be so restricted that shifting would be 
unnecessary. 

The work is then put into a heated screw press, 
such as the vulcanizing and matrix press, and is 
dried for a period varying from some minutes up to 
half an hour. Some blotting paper is advanta- 
geously pressed on top of the whole in the press 
while drying. The press is opened, the flong re- 
moved, and dried in an oven. It is kept under a 
piece of wire net while drying to keep it fiat. The 
net may be of wire, .064 inch thick, with six 
meshes to the inch. This baking is not strictly 
necessary for rubber stamp work. 

This gives a matrix which may be used as rub- 
ber stamp moulds. In use it is recomended to 
place a piece of smooth tin foil over it. This tends 
to give a smoother surface to the rubber. 

STRUCK UP MATRICES. 

Didot^s polytype process may be advantageously 
used for producing type metal matrices. The fol- 
lowing is the method of applying it. 

The type form is firmly locked and is backed up 
by and secured to a solid block of wood. It is sus- 
pended in a sort of gallows frame with the face of 
the type downward and exactly level a few inches 
above a table. Underneath it a shallow tray is 



AND THE MANIPULATION OF RUBBEB^ 83 

placed^ into which some melted type metal is 
poured. The melted metal is carefully watched. 
The block and type are held by a catch so as to be 
released at will. Just as the type metal is on the 
point of solidifying, the block is released and drops 
upon the metal in the tray. The type should be 
slightly oiled. The force of the blow produces a 
matrix in the metal, and the form can at once be 
removed. 

It is well to have accurately adjusted distance 
pieces for corresponding striking pieces on the type 
block to impinge upon. The process is highly 
spoken of, especially for small forms such as those 
mostly required for rubber stamps. 

CHALK PLATES. 

The base for this form of matrix is a metal 
plate whose surface is slightly roughened with sand- 
paper. It is next rubbed over with white of egg, 
and flooded with the chalk wash made as follows: 
Flong paste (described under Papier Mache Ma- 
trices, page 80), six ounces; whiting, twenty-four 
ounces; water, three pints. The whiting is softened 
by soaking for an hour or more. The whole must 
be intimately mixed. It should cover the plate to 
the depth of one-thirtieth to one-twentieth of an 
inch. The plate is dried in a perfectly horizontal 
position. 

When dry the design or writing, etc., is made 
with a smooth steel point, the lines being carried 



84 RUBBER HAND STAMP MAKING, 

clear through the white layer to the metal. The 
mould is now baked at a temperature well above 
boiling water; as high as 392° F. (200° C.) may be 
reached without harm. 

If the coating seems too tliin^ an extra coat can 
be given between the lines especially over the larger 
areas. This must be done before the baking. A 
pipette may be used for putting on this coat. This 
deepening has the bad effect of increasing the 
chance of the coating stripping from the metal. 

The matrix thus prepared is used in the press 
just as is the ordinary plaster matrix. It is suited 
for reproduction of autographs, scrip, diagrams, 
etc. 



. CHAPTER IX. 

THE MAKING OF YAKIOUS SMALL ARTICLES OF INDIA 

RUBBER. 

India rubber can be so readily shaped in moulds 
and the latter are so readily made of plaster of paris 
that any one who is interested in such things will 
find endless amusement in working out different 
designs. Before suggesting any specific articles 
the following are the general points to be kept in 
mind. 

The material may be uncured mixed sheet of any 
thickness. As we have seen this material w^hen 
heated and pressed runs together. It can be forced 
into any shape by comparatively slight pressure. 
So exactly does it reproduce the smallest line or 
mark^ that care must be taken to have the moulds 
very smooth and free from defect. Powdered soap- 
stone is used to prevent adherence to the mould, but 
great care must be taken not to mix it among the 
pieces of the India rubber, where several are used 
in one article, as it will prevent their coalescing 
or running together. 

Another point is to contrive to introduce the 
proper quantity of rubber. The aim must be to 



86 liUBBEB HAND STAMP MAKING 

liave a slight excess, but to avoid waste this should 
be as little as possible. Unless some rubber is 
squeezed out there is no certainty tliat the mould 
has been filled. Any projecting ''fins'' from the 
overflow are cut off with a knife or scissors after the 
article is removed from the mould. 

Plaster of paris or dental plaster mixed with dex- 
trine or gum arable water or the zinc oxychloride 
cement, already described, is to be recommended for 
the moulds. They should be made, if deep, in 
frames or '' flasks '' of tin, as plaster if unsupported 
is liable to split open when the rubber is forced home. 
For many articles the hot press can be used.. 
Such articles are mats and other thin flat pieces. 
The rubber stamp sheet is a good material for them. 
For thicker articles a thicker sheet can be used, and 
sheet of any gauge can be procured from the maker. 
Much of what has been said about India rubber type 
applies to the making of miscellaneous shapes. It 
will also be understood where wooden moulds are 
spoken of that plaster, or, still better, metal can be 
substituted, and is to be recommended for nice 
work as the grain of the wood is very apt to show 
where the India rubber comes in contact with it. 
' Suction discs and similar small articles into which 
an extra thickness of India rubber .enters are best 
cured in a vulcanizer. The flower pot arrangement 
is excellent for such. The time for curing may 
be somewhat extended on account of the greater 
thickness of material to be acted on. 



AND THE MANIPULATION OF RUBBER, 87 

Suction Discs, — For suction discs a mould is 
required which will produce a shallow cup with the 
edge feathered or reduced to a very slight thickness. 
Its outer surface should be raised in the centre so 
as to give a projection for attachment of the hook. 
The discs are generally made small^ not over an inch 
in diameter, as they are not reliable for any heavy 
service. Their principal use is to suspend advertis- 
ing cards and light articles to the glass of show 
windows. The following is a method of making a 
simple mould. 

A hole to give the outside contour should be 
bored in a small piece of wood. A marble which 
will exactly fit the hole is next required. Some 
plaster vt paris is mixed with water and put into the 
bottom of the hole, and the oiled marble is pressed 
down until the plaster rises and fills the entire space 
under the marble. After it has set the marble is 
removed. The proportions should be so arranged 
that the plaster will have risen at the sides within 
an eighth of an inch of the surface of the wood. 
This gives the exterior mould. For the cup or 
hollow a marble a shade too large to enter the 
hole may be used. 

One or if necessary two thicknesses of mixed 
sheet rubber cut into disc shape so as to fit the 
hole are inserted in the block, and the larger marble 
is placed on top and screwed down by the press. 
Heat is now applied in the vulcanizer. When the 
thermometer indicates 212° F. (100° C), or better a 



88 



RUBBER HAND STAMP MAKING 



little more^ the mould is withdrawn and the screws 
turned until the rubber is forced down and the 
excess begins to squeeze out between the marble and 
the wood, which two should now nearly touch. It is 
replaced and the heat is brought up to the curing 
temperature 284^ f. (140° C). It is possible that 
a second screwing up may be needed. The spring 
press is in such cases particularly convenient as it 
avoids the necessity for re- 
moving the press from the 
vulcanizing chamber. After 
half an hour it will be thor- 
oughly cured. A hole is 
made through its centre from 
side to side thereof, but not 
penetrating the disc, and 
through this hole a brass 
nail is thrust and bent into 
hook form. 

In the cut the correct shape for the mould and 
consequently for a suction disc is shown. This can 
be easily secured where a disc already made is procur- 
able by casting in plaster, or, with a little iiigenuity 
the template for the mould and the plunger to be 
used instead of the marble can be whittled out of 
wood. The lower body of the mould in such a case 
can be made of plaster of paris. To secure the 
alignment of the two parts of the mould, dowel pins, 
indicated in dotted lines, should be placed near the 
periphery. The gum should be introduced in a lump 



4 


m 


MM. 



Mould for Suction Discs. 



AND THE MANIPULATION OF EUBBEB. 89 

near the centre^ in order that it may sink well down- 
wards to the bottom of the mould before spreading 
laterally. Sometimes the tips have a recessed 
end. This is secured by the use of a mandrel^ 
shown in dotted lines in the axis of the mould. 
Such discs are sometimes made to be cemented to 
arrows to be discharged against smooth surfaced 
targets^ to which they adhere on impact by atmos- 
pheric pressure^ giving rise to a very interesting 
game. 

Another use of suction discs is as photographic 
negative holders. They can be fastened to a wooden 
handle and be attached by suction to the back of 
a negative under treatment. For this purpose they 
should be at least two inches in diameter. 

Pencil Tips. — These are generally little cylinders 
of India rubber^ which fit into a tube that slides 
over the end of the pencil. They can be thus sim- 
ply made. A hole is bored in a piece of wood the 
diameter of and a little more than the depth of 
the pencil tip. A short cylinder that exactly fits 
the hole is required for plunger. The gum is put 
into the hole in little discs^ or rolled up into a 
cylinder^ the plunger is placed on top, and the 
mould put in the press. It is shaped by pressure 
and cured as described. 

Sometimes the tips are cup shaped. For these 
the mould is made in two sections fastened by 
catches or by pins set in the plaster as shown in the 
cut. The hole is made larger at bottom than at 



so 



RUBBER HAND STAMP MAKING 



top, and at the top is a little smaller than the shaft 
of the pencil. A plunger that nearly fits the small 
end is provided. The india rubber is placed in the 
mould and heated. When soft, the plunger is 
forced down to the proper distance in the press 
and the article is cured. Care must be taken to 




Mould for Pencil Tips. 

give the plunger a good coating of talc, and it must 
be made to sit vertically. The arrangement of a 
cylindrical hole shown in the cut secures this result 
perfectly. As distance piece a pin is passed through 
the plunger. 

Cane and Chair Leg Tips, etc. — By carrying out 
the process just described with larger moulds and of 
slightly different section very convenient tips for 
chair legs and walking canes can b'e made. Such 
tips can be modified in size and thickness to answer 
as covers for the mouths of bottles^ test-tubes, etc. 

Corlcs. — These may be made in moulds tapering 



AND THE MANIPULATION OF BUBBEB. 91 

from top to bottom. The India rubber must be 
packed in with great care to secure as solid filling as 
possible. A plunger is used that enters the larger 
end and is a very little smaller in diameter, so as to 
descend a little way into the mould. This distance 
determines the- length of the cork. As the perim- 
eter of the plunger strikes the wails of the mould 
it cuts off almost completely the excess of rubber 




Mould for Rubber Corks. 



that has squeezed up past it. An /excellent modifi- 
cation of the mould is shown in the cut. The 
upper part with parallel sides serves as a guide for 
the plunger. It is a similar extension as the one 
recommended to be used for the plunger in the hol- 
low pencil and chair leg tip moulds just spoken of. 

Mats. — These may generally be made in the hot 
press. Designs for them in great variety may be 
found in cut glass and pressed glass dishes. Many 



92 RUBBER HAND STAMP MAKING 

of these have patterns on their bottoms that can be 
moulded in plaster to serve as matrices. 

Cord, Th^'ead mid Seamless Tube. — By placing the 
mixed India rubber in a cylindrical mould titted 
with piston and with one or more round holes in the 
bottom, the material may be softened by heat and 
forced out of the lioles by depressing the piston. 
This will form cylindrical thread or cord. As it 
descends it may be received in a box of powdered 
talc and be afterwards cured. By providing the 
hole with a mandrel seamless tubing may be thus 
made. In making such the mandrel usually re- 
mains in place during the curing. Plenty of 
powdered talc must be used. 

Skeletonized Leaves as Models. — Tliese would form 
interesting models from which matrices could be 
made in plaster. It would be possible to produce 
some very pretty stamps or mats from these and 
similar models. 

After some experience inspection of any article 
will show how it was moulded. The fin will indi- 
cate the joint in the mouldy and with this as a clew 
the mould can be almost certainly constructed like 
the original. 

'India Rubber' Bulbs, — Bulbs and hollow articles 
generally, such as dolls, toys and the like, cannot 
be made without special high pressure hollow 
moulds. The general process consists in cutting 
out gores from mixed sheet as for a balloon. The 
edges are coated with cement (thick benzole or car- 



AND THE MANIPULATION OF BUBBER. 93 

boil disiilphide india rubber solution) and while 
the rubber is warm the seams are jjressed and 
knitted together with the fingers. A hole is left in 
one place through which some pure water or water 
of ammonia is introduced. The bulb is now blown 
up with the mouth or otherwise^ and while inflated 
the hole is pressed shut. This is often done with 
the teeth. Any projections around the seams are 
cut off with curved scissors. The mould is of iron 
and in two halves. Powdered talc is applied^ and 
the bulb is placed in and shut up in the mould 
which it should exactly fill. The mould is clamped 
together and the whole is put into a vulcanizer, and 
the rubber is cured. The steam and vapor formed 
by its liquid contents expand it and press it with 
great force against the sides of the mould. After 
curing the mould and bulb are removed from the 
vulcanizer, cooled by a shower bath of cold water^ 
the mould is opened and the bulb is removed. Often 
an iron pin is left projecting through the side during 
the vulcanizing; which pin^ when withdrawn^ leaves 
the necessai:y aperture, or it is perforated. The bulbs 
are polished by tumbling in a revolving cylinder. 
Considerable skill and practice are needed to succeed 
in making hollow bulbs. Great accuracy is needed 
in cutting out the gores and in joining the seams. 



CHAPTER X. 
THE manipulatio:n^ oe masticated sheet eubber. 

The manipulation of pure sheet rubber is simple^ 
yet is liable to lead to disappointment. When two 
pieces are laid face to face and cut across with a 
sharp knife, or scissors, the edges will adhere with 
considerable tenacity. This may be increased by 
applying some thick solution of India rubber in a 
volatile solvent, and by manipulating the sheets so 
as to bring the entire surfaces of the cuts together. 
Finally the material may be charged with sulphur 
by absorption or by Parkes^ process, and cured in 
a glycerine or calcium chloride bath, all of which 
are described in chapter XI. The same treat- 
ment will affect the cement used in making 
the joint also, bringing about its vulcaniza- 
tion. 

Such in a few words is the main process in the 
treatment of this class of goods. Where it is de- 
sired to prevent adherence, soapy water or powdered 
talc is used. 

Adherence may be produced between the surfaces 
of the sheets if they are clean, by pressure and a 
little warmth. The method of making toy balloons 



THE MANIP ULA TION OF B UBBER. 95 

will give an example of how the article is dealt with 
by the manufacturer. 

A pile of pieces of masticated sheet rubber is 
made. Every piece has one side coated with pow- 
dered talc, and two talc-coated sides are placed in 
contact in each "pair. As they are piled up, the 
outer surfaces of each pair are moistened with 
water. A steel punch or die, pear shaped in out- 
line, is used to cut down through the pile, cutting 
all the pieces into that shape. 

The pile is then taken apart in pairs. The separa- 
tion takes place between the wet surfaces, the edges 
of each pair adhering slightly so as to enclose the 
talc-coated surfaces. The neck is opened if neces- 
sary. A rather weak or thin solution of India rub- 
ber in benzole is now brushed over the freshly cut 
edges. By pulling out the centre of each piece the 
edges are brought into contact, and adherence is 
produced. 

If the Parkes process of vulcanizing, chapter XI., 
is employed they are cured to the slight extent nec- 
essary upon a tray coated with talc. The balloons 
are then ready for inflation. 

They are rather delicate articles to make except 
for immediate use as the thin material is liable to 
become over vulcanized. 

In the chemical laboratory sheet rubber can be 
used for covering the ends of glass stirring rods. 
These answer very nicely for cleaning out from 
beakers the last particles of a precipitate. The 



96 BUBBLE HAND STAMP MAKING. 

sheet is cut of proper size and is bent around the 
end of the rod and cut off close with a pair of scis- 
sors. It adheres where cut. It is then pinched 
with the fingers to bring the edges into better con- 
tact and the operation is complete. A slight heat 
makes it adhere better. 

To connect glass tubes in setting up laboratory 
apparatus the same material was formerly used. It 
was wrapped around the joint, tied with thread and 
slightly warmed. At present this form of connec- 
tion is wholly displaced by ready made rubber 
tubing. 

It is interesting to observe in all articles made 
from this sheet the marks of the original cutting 
knife. These may be observed in inflated balloons, 
as parallel lines running all over the surface, and 
magnified by the expansion due to the inflation. 



CHAPTER XI. 

YAEIOUS VULCANIZING AND CURING METHODS. 

The regular methods of vulcanizing and curing 
can be departed from and good results obtained. 
A few excellent methods differing essentially from 
the ordinary ones are described which Avill be of 
service to workers on the small scale, as they enable 
one to dispense with vulcanizer and air bath en- 
tirely. 

One type of curing process does away with the air 
or steam vulcanizer, and substitutes, as the curing 
agency, a hot bath of liquid. For this purpose a 
fluid is required that will not act injuriously upon 
the india rubber, and which will give a curing 
temperature without boiling away. One favorite 
liquid is glycerine. This can be heated to the nec- 
essary degree and is an excellent substitute for the 
expensive apparatus often used. For exj)erimental 
work it is exceedingly convenient. 

In use it is placed in a vessel of proper size 
and a thermometer is suspended so that its bulb 
dips into the liquid near one side and does not 
touch the bottom of the vessel. The heat is applied 
by a gas burner, alcohol lamp or oil stove. Of 



98 RUBBER HAND STAMP MAKING 

course the vessel may be placed on an ordinary 
cooking stove or range^ and the heat may be gradu- 
ated and adjusted by moving it about until it 
reaches a part of the stove where the proper heat 
will be maintained. 

The mould with its contents is immersed in the 
glycerine, care being taken to see that it so placed 
as to assume the mean temperature of the liquid 
and not to be heated too hot. This might happen 
if it stood on the bottom of the vessel, so it is well 
to have it supported or suspended a little above 
it. 

It is easy to see that the whole may be so arranged 
that the screw handle or pressure nuts of the mould 
will rise above the liquid. In this case the press 
can be screwed down while the article is heating. 

Instead of glycerine a strong solution of some 
salt in water has been recommended. A solution 
of calcium chloride, or some other salt can be sub- 
stituted. Either are very cheap and will be quite 
satisfactory. 

Another treatment which applies also to the mixing 
operation is by the sulphur bath. Sulphur is melted 
in an iron vessel and brought to a temperature of 
248° F. (120° C). A piece of unmixed pure caout- 
chouc immersed in this bath will gradually absorb 
sulphur. The case is almost parallel with the 
absorption of water or benzole by the gum. The 
piece swells and thickens as it is acted on and 
eventually will contain enough sulphur for vulcani- 



AND THE MANIPULATION OF RUB BEE. 99 

zation. It may absorb as much as fifty per cent. 
The point of proper absorption must be settled 
more or less empirically or by successive trials. 
. After enough has been taken up the piece is re> 
moved and dipped into cold water, which cracks the 
adherent sulphur .so that it can be brushed or rubbed 
off. This gives a piece of mixed rubber ready for 
moulding and curing. It can be heated and 
moulded and may be cured as desired, in a liquid 
bath, hot press or vulcanizer. 

It will be observed that this provides for the ad- 
mixture of sulphur only; no talc or other solid can 
be thus introduced. The addition of these solids 
tends to make the rubber of a more attractive color 
and their use is not to be deprecated in all cases. 
Hence the sulphur bath process is not to be consid- 
ered a perfect one. 

In the sulphur bath the mixing and curing 
processes can be combined. If the liquid sulphur is 
heated to the vulcanizing temperature, 284° F. 
(140° C), a thin strip of gum immersed in it will 
be vulcanized completely in a few minutes. A 
heating of several hours at the lower temperature 
will effect the same result. 

The sulphur bath processes must be regarded as 
unsatisfactory. It is not easy to feel that any de- 
pendence can be placed upon them as regards re- 
liability or constancy <ff product. The sulphur also 
will mostly effect the surface. Thin pieces may be 
satisfactorily treated, but the same confidence can- 



LofC. 



100 RUBBER HAND STAMP MAKING 

not be felt as is experienced when specific amounts 
of ingredients have been mixed in with pure caout- 
chouc in a regular mixing* machine. 

The sulphur bath is of value to the experimenter, 
enabling him to do his own mixing without expen- 
sive apparatus. 

Bromine, iodine, chlorine and nitric acid are vul- 
canizers. A piece of sheet rubber dipped into 
liquid bromine is instantly vulcanized. Iodine and 
nitric acid have also been used in commercial 
work. 

Alkaline or alkaline earth sulphides can be em- 
ployed in solution under pressure for vulcanizing. 
At a vulcanizing temperature their solutions will 
answer for thin sheet very well. Polysulphides of 
calcium have thus been employed. 

By simply lying embedded in finely divided sul- 
phur at a temperature of 233° P. (112° C.) as much 
as ten per cent, of sulphur may be absorbed by thin 
sheet rubber. This is one of the processes pecul- 
liarly suited for work on the small scale. It may be 
used instead of the Parkes process next to be de- 
scribed. 

Chloride of sulphur is an orange red mobile 
liquid of a peculiar and disagreeable odor. It boils 
at 276'"' P. (136° Co). It dissolves both sulphur and 
chlorine so that it is not easy to obtai-n it in a pure 
state. If unmixed India rubber is exposed to its 
action it will quickly become vulcanized. At ordi- 
nary temperatures the mixing action takes place. 



AND THE MANIPULATION OF RUBBER. 101 

though it is much accelerated by a slight applica- 
tion of heat. 

It is quite possible that this action may be of use 
to the reader in his manipulation of India rubber. 
Thin sheet may be vulcanized by being immersed in 
a solution of this substance in bisulphide of carbon 
followed by slight heating. The thin layer of 
caoutchouc left by evaporation of the chloroform 
solution of india rubber may thus be vulcanized so as 
to become comparatively strong and elastic. Where 
the same solution has been used as a cement or for 
patching overshoes and finishing the patchy a vul- 
canization can thus be given to it. 

The process is known as Parkes^ cold curing pro- 
cess. 

A solution of one part of chloride of sulphur in 
forty parts of bisulphide of carboil is of good 
strength for rapid work. A thin article needs but an 
instant of immersion. It then is placed in a box or 
tray upon some talc powder and is heated to about 
104° F., (40° C). One minute of curing will suf- 
fice. It is advisable to wash off the articles after- 
w^ards in water or in weak lye to remove any traces 
of acid. 

Petroleum naptha can be used as the solvent in- 
stead of bisulphide of carbon. The latter substance 
has an exceedingly disagreeable odor, and its vapors 
must be considered rather injurious especially to 
those who are not accustomed to them. 

When thick articles are to be cured* by this pro- 



102 BUBBER HAND STAMP MAKING, 

cess a much more diluted solution is used. One 
per cent, or less of the chloride of sulphur is the 
proportion used. The object of this is to enable 
a longer immersion to be employed so that the in- 
terior will be affected before the outer layers become 
too much charged with the vulcanizing material. 

In this short description of the Parkes curing 
process hints for a useful method may be found. 
The process is beyond doubt by far the simplest 
known for treatment of India rubber. Exactly 
what reaction takes place is unknown. Whether 
the sulphur or the chlorine is the acting vulcanizer 
has not as yet been determined. 

Its defect is that it produces surface action, anal- 
ogous to casehardening. One method of avoiding 
this is to remove the articles from the sulphur 
chloride bath and at once to immerse them in water. 
This prevents the rapid volatilization of the solvent 
and an equalizing of the absorption ensues. 



CHAPTER XIL 

THE SOLUTIOI?^ OF IKDIA RUBBER. 

India rubber presents some difficulties in its 
solution. If a piece of pure gum just as received by 
the factory is placed in hot water it will swell and 
whiten after a while^ but will not dissolve. If a 
similar piece is placed in benzole a similar but 
greatly exaggerated action takes place. The piece 
if left to soak for a day or more swells enormously, 
but very little solution is effected. 

The swollen india rubber can be removed from 
the benzole in a single piece. It will display all the 
layers and marks of the original piece which was 
perhaps of not one hundredth part of its volume. 
Some parts will be a perfect transparent jelly. 

It has been found that masticated india rubber 
dissolves with comparatively little difficulty. If 
the experimenter will place in a porcelain mortar, 
the jelly-like mass obtained as above detailed, and 
will rub it up thoroughly, it will be effectually mas- 
ticatqd. This requires a little patience, as the 
slippery material seems to elude the pestle. Yet 
eventually it will all be reduced to a perfectly homo- 
geneous mass. Its action while being rubbed rip is 



104 RUBBER HAND STAMP MAKING 

very peculiar. At first no progress seems to be 
made. After a little the lumps yield to the friction. 
The rubber then begins to attacli itself to the pestle 
and mortar, and begins to be drawn ont into ever 
changing webs and threads. As the operation ap- 
proaches completion the material makes a snapping, 
crackling noise familiar to all rubber workers. 
When complete there will be no lump left, and the 
whole will be a uniform pulp. 

If benzole or a volatile solvent lias been used, the 
rubber will easily be removed from tlie mortar with 
a spatula or palette knife. If turpentine was the 
solvent it will be impossible to remove the last 
traces except after long standing or by solution. 

If replaced in the original solvent it will now come 
into nearly or quite perfect solution. This is the 
best way of masticating on the small scale. It is 
almost impossible to masticate untreated gum in an 
ordinary mortar. 

The dealers sell a special India rubber for the 
manufacture of cement and solutions. This is so 
treated by mastication that it dissolves with great 
readiness. It is also said that heating under pres- 
sure is used to dissolve it in some factories. 

.Many solvents have been used and none work 
without some difficulty. Benzole, coal tar naptha, 
petroleum naptha, carbon disulphide, ether and 
chloroform, oil of turpentine and caoutchoucin are 
the best known. The naptha best suited for its 
solution is termed solvent naptha. It has a specific 



AND THE MANIPULATION OF RUBBER. 105 

gravity of .850 at 60° F. (15>^° C); it boils at from 
240° F. (115>^^ C.) to 250" F. (121° C.) and on evap- 
oration should leave no more than ten per cent, of 
residue at 320° F. (160° C.) 

Payen recommends a mixture of 95 parts bisulph- 
ide of carbon with 5 parts of absolute alcohol. 

Commercial chloroform is apt to be too impure to 
act as a good solvent. It is apt to contain alcohol 
mixed with it as a preservative^ which impairs its 
effectiveness. 

Some of these solutions are better suited than 
others for the deposition of thin layers by evapora- 
tion.. Turpentine gives a very sticky and unman- 
ageable solution^ which dries very slowly. Payen's 
solution and the chloroform and the benzole solu- 
tions may be cited as especially adapted for this 
purpose. Careful vulcanization by the cold curing 
method can be applied to articles made by such 
deposition from evaporation. 

In the case of all of them some form of mastication 
for the India rubber is needed. The simple mortar 
grinding of the gum SAvelled by the solvent is the 
only practical treatment without special apparatus. 

When it is remembered that fixed oils are de- 
stroyers of vulcanized or un vulcanized india rubber 
it will be obvious how important it is to use pure 
solvents. Too great care cannot be taken to pre- 
serve the liquids pure and free from such matter. 

A solid hydrocarbon may be used. Thus paraffin 
wax, such as candles are made of^ when melted acts 



106 RUBBER HAND STAMP MAKING 

as a solvent. The resulting liquid solidifies when it 
cools^ retaining an almost greasy feel. 

Boiling oil of turpentine is reconrimended Ly 
some for the solution of vulcanized India rubber. 
Phenyle sulphide^ it is stated, wi]] soften it so as to 
render it workable. The latter discovery is credited 
to. Dr. Stenhouse. 

It is stated that a solution or pasty mixture of 
one part of caoutchouc in eleven parts of turpentine 
with one half part of a hot concentrated solution of 
sulphur (potassium sulphide) gives on evaporation a 
film neither tacky nor soft, a species of vulcaniza- 
tion taking place. 

It is of much interest to note that an aqueous 
solution of India rubber has been proposed in which 
the vehicle is a solution of borax in water. This is 
well known to be a solvent for shellac and other 
resins. It has been recommended often as a vehicle 
for rubbing up India ink. The ink made by mixing 
lampblack with the shellac solution is nearly water- 
proof. A shellac varnish is given by the plain solu- 
tion. 

The experiments upon india rubber were pub- 
lished in a recent trade paper. One method of 
making the solution is as follows. 

A solution of borax two fifths saturated is made 
by adding to two volumes of saturated solution 
three volumes of water. To this is added a solution 
of india rubber in benzole or other hydrocarbon of 
such strength and in such quantity as to contain 



AND THE MANIPULATION OF BUB BEE. 107 

from three and one-half to four and one-half per 
cent, of India rubber referred to the borax solution. 
It is now vigorously shaken and heated to 120°-140° 
P. (49°-60° C.) and the agitation, not too violent, is 
continued until it cools. Ceara or Madagascar rub- 
ber answers best; Para is not so good for this for- 
mula. This may be termed tlie indirect or emul- 
sion method. 

For direct solution from two to three volumes of 
water may be added to three volumes of saturated 
borax solution. The India rubber is added in ex- 
tremely thin shavings and the solution is heated. 
For weak solutions the boiling point need not be 
reached. For strong solutions the heating should 
be done under pressure so as to bring up the j)res- 
sure to one to three atmospheres. 

Such solutions msij contain as much as eight per 
cent, of the gum. The mixture is liable to coagu- 
late or gelatinize just at the wrong time, but it may 
be of value as a vehicle or as a waterproofing agent. 
It deserves further investigation, which it is to be 
hoped it will duly receive. 

G-reat care is necessary in working with naptha, 
benzole, carbon disulphide and similar liquids. 
Their vapor is given off at ordinary temperatures 
and may travel some distance to a lamp or fire and 
become ignited and carry the flame back to the ves- 
sel. Their vapors are also anaesthetic and should be 
avoided as regards inhalation. 



CHAPTER XIIL 

EBONITE, VULCANITE AND GUTTA-PERCHA. 

Ebonite and Vulcanite. — These two well known 
substances are India rubber, in which the vulcaniza- 
tion process has been intensified. From twenty- 
five to fifty per cent, of sulphur is added in the 
mixing, and the curing is prolonged to several 
hours. A temperature of 275° F. (135° C.) for six 
to ten hours is sometimes recommended, but gener- 
ally a shorter period at the regular temperature, 
284° F. (140° C), may be employed. 

The mixed sheet is made and sold extensively for 
dentists^ use. It' is soft and flexible and very easily 
moulded. It is treated like the regular mixed sheet 
in every respect, except that plumbago brushed on 
the slightly oiled surface of the mould is recom- 
mended instead of the light colored talc, to prevent 
adherence. Wax where available is better than 
oil. 

Sometimes specimens are built up in sections. 
About an hour before full vulcanization in the 
fourth stage, new material can be added and will 
attach itself to the old. The stages of vulcaniza- 
tion are thus given by Bolas. 



AND THE MANIPULATION OF RUBBEB. 109 

'^ Several distinct stages or steps may be traced 
during the curing of ebonite; and I wish to call 
your attention to some specimens illustrating these 
various stages. 

^'Here^ in the first place, is the plain mixture of 
sulphur and rubber, this being nearly white, and 
capable of becoming quite plastic or soft by the ap- 
plication of a gentle heat. 

" The second specimen illustrates the action of a 
very moderate degree of heat on the mixed material, 
this particular sample having been heated to 128° 
Centigrade for twenty minutes. It is, as you see, 
somewhat darkened, and has lost a little of its orig- 
inal softness; while a degree of heat which would 
have rendered the original mixture plastic, like 
putty, fails to make much impression upon it. 

''The third specimen illustrates the effect of a 
more prolonged heating, this sample having been 
heated for an hour to 135° Centigrade. It is olive 
green in color, and has acquired a certain amount 
of elasticity, resembling that of • a rather inferior 
quality of vulcanized caoutchouc. 

''The fourth stage of curing is illustrated by this 
specimen, which you see is brown, and tolerably 
hard. Ebonite in this state refuses altogether to 
become plastic by heat, and a temperature of 150° 
maintained for half an hour or less would suffice to 
bring it to the fifth stage, or that of finished 
ebonite. 

" The fifth stage, or that of properly cured 



110 RUBBER HAND STAMP MAKING 

ebonite^ is the goal to be arrived at in manufactur- 
ing the material. There should be no places where 
the curing is imperfect, a kind of defect which is 
likely to happen when articles of unusual thickness 
are vulcanized, and no portion of the ebonite should 
be spongy or honeycombed by air bubbles. 

^' The sixth, or spongy state, is generally the 
result of over-heating, bubbles of gas forming in 
the material, and converting it into a kind of 
porous, cinder-like mass. 

'^A specimen will now be handed round, which 
illustrates the third, fourth, fifth and sixth stages, 
as already described. The specimen in question 
was cured on a hot plate, this having probably been 
heated to 160° or 170° Centigrade; and you will be 
able to trace all gradations in the curing operation, 
from the first setting of the plastic material to the 
destruction of the ebonite by overheating.^^ 

Cement for uniting pieces of the partially cured 
material may be made by rubbing up some of the 
untreated scrap with benzole. 

At the heat of boiling water, ebonite can be bent 
to a certain extent, which bend it retains on cooling. 
When warm an impression of a coin or relief die 
may be made on it by heavy pressure which it will 
retain. On heating the image disappears. If before 
heating the surface is planed off and the piece is 
heated the image formerly in intaglio will expand 
into relief. 

By the exact process of rubber stamp making 



AND THE MANIPULATION OF RUBBER. Ill 

excellent stereotype plates may be made of eb- 
onite. 

It can be turned at high speed in a lathe and pol- 
ished with fine 000 emery paper followed by a cloth 
bob with rotten stone^ etc,,, and water or oil. Blot- 
ting paper, charged with the above or with tripoli, 
is excellent for polishing small surfaces by hand. 

Ebonite is a good connecting material between 
softer rubber and iron, the whole being vulcanized 
together ; the iron should be well roughened or 
cut into rasp-like or file-like projections. 

Ebonite is properly the name for black hard rub- 
ber, and vulcanite for the colored products such as 
used by dentists and others. 

GUTTA-PERCHA. 

Gutta-percha is prepared by coagulation from the 
juice or sap of several trees, among others the 
Isona7idra gittta, of Borneo and the East Indian 
Archipelago. The product gutta-percha is iden- 
tical in composition with India rubber. It is hard 
at all ordinary temperatures. 

Its manufacture includes purification and masti- 
cation. It is far more amenable to treatment than 
is india rubber. Many materials are mixed with it 
as adulterants or otherwise in the factories. 

It is more useful in the form of sheets. These 
when heated to 122^ F. (50° C.) become pliable and 
can be moulded by pressure to any degree. At the 



112 RUBBER HAND STAMP MAKING 

temperature of boiling water it becomes pasty and 
adhesive, and at 266'' F. (130^ 0.) it is so soft that it 
may be considered as melted. 

It is an admirable moulding material. Stereo- 
types and other relief or intaglio images can be 
made by pressing it Avhile heated. These are often 
absolutely perfect reproductions of the original. 

Dishes for photographic purposes, etc., are easily 
made out of the sheet. By gentle warming they 
become pliable, and a greater heat makes surfaces 
capable of adhering by pressure. 

Tubes can be made by the squirting process, as 
used for india rubber. Wires are coated with it in 
a similar manner. ' 

It has several defects. It is not durable if ex- 
posed to the air with consequent changes of temper- 
ature. It is also too easily softened by heat, as of 
course no hot liquid can be introduced into a gutta- 
percha vessel. The Parkes cold curing process can 
be applied to it, which makes it more indifferent to 
heat. This is applied by dipping an instant and 
drying. After several repetitions the period of dip- 
ping is prolonged and ultimately it is left immersed 
some time. If left immersed at first it would dis- 
solve. 

It is soluble in most caoutchouc solvents, particu- 
larly in carbon disulphide. 



CHAPTER XIV. 

GLUE OR COMPOSITION^ STA3IPS. 

Stamps made from a mixture of glue, glycerine, 
and molasses or from similar mixtures are an excel- 
lent substitute for iridia rubber stamps. Properly 
made they possess all the flexibility that character- 
izes the rubber ones, while for fatty inks such as that 
used by printers and lithographers, which inks tend 
to destroy rubber stamps, they are much better. 
They are adopted by the United States government 
for making dating stamps for use in the Post Office 
Department ; by publishers of directories for print- 
ing advertisements on the edges of their publica- 
tions, and in many other cases. Our description 
shall follow as closely as possible- the process and 
methods used in the United States Post Office. 
They are there termed ^'composition blotters.''^ 

The composition of which they are made is print- 
er's roller material, l^ine and one-half pounds of 
fine quality glue are soaked in just enough soft 
water to cover it until it is thoroughly softened. 
It is then melted. In the Government Department 
a steam kettle is provided for the purpose. An 
ordinary glue pot will answer for smaller quantities. 



114 



RUBBER HAND STAMP MAKING 



When melted four and one-half pounds of best molas- 
ses and seven pounds of glycerine are added^ and the 
whole is thoroughly mixed. The formula varies a 
little according to the prevailing temperature, less 
molasses being added when the weather is warm, and 
vice versa. Experience is here the best teacher. 
When well mixed it is poured out into tin pails 
whose inner walls or sides and bottom have beeu 




Model for Composition Stamp Mould. 



rubbed over with oil. It solidifies in cooling and 
becomes a clear brown jelly quite free from any 
stickiness or superficial moistness. 

In use it is turned out of the pails to which, 
owing to the oiling^ it does not adhere. It is cut 
off as wanted, melted by heat and cast in oiled 
moulds. 

The latter are made of type metal to which one- 
third its weight of lead has been added. As model 



AND THE MANIPULATION OF RUBBER. 115 

for the mould or matrix a brass model of the 
stamp is employed. This represents a sort of oval 
based cut-off or truncated cone^ about an inch 
high and a little over an inch long on its base. A 
flange extends outward from its base and a tube is 
provided to fit this flange. Its smaller end corre- 
sponds to the face of the stamj), and on it are en- 
graved in full relief any permanent characters. 




Composition Stamp Mould. 

circles or border lines, etc. Through its centre one 
or more apertures are made. Into these, changeable 
steel, iron or brass type may be introduced and set 
fast with plaster of paris. 

To make the mould, the brass model with its mov- 
able type set as required is placed upon aflat table 
or plate, face upward, and surrounded by the tube, 
as shown in partial section in the cut, page 114. The 
tube is a strip of sheet iron, which is bent around the 
flange and is secured in place by a wire twisted 
around it. The melted alloy (type, metal and lead) is 



116 RUBBER HAND STAMP MAKING 

poured into the space thus formed until it rises a 
quarter of an inch above the face of the model. In 
a few minutes it sets and is removed and allowed 
to cool. This gives a cup with the inscription and 
design depressed or in intaglio upon its inside base. 
This is shown in the cut, page 115, partly in section; 
it will of course be understood that the mould forms 
a complete cup. 

To make the stamp the interior surface of the 
mould is oiled wuth a stiff brush. It is not material 
what oil is used. The composition melted by heat is 
then poured into the cup, and is allowed to solidify. 
Owing to the conical shape of the mould it is 
readily removed. The mould must be hot but not 
too much so. 

In the Post Office stamps the date requires to be 
clianged frequently. Some of the figures do duty 
for two or three days each month. Thus the figure 
8 is in the designation of three days, the eighth, 
eighteenth, and twenty-eighth. There are three 
changes involved therefore in connection with this 
day numeral. When a stamjD mould or matrix is cast 
the place of numerals that are to be changed is 
filled with a blank space in the part where the type 
would otherwise come. A number is stamped in 
this space when needed, by means of an ordinary 
steel number-punch. 

When the number is to be changed the old char- 
acter is scraped or cut out, leaving a small irregular 
hollow. A very small piece of soft lead, about one- 



AND THE MANIPULATION OF BUB BE It 1 1 7 

sixteenth of an inch on each side, is dropped into 
the holloAV. With a flat faced punch it is flattened 
out, and on it the new number is impressed by a 
steel punch. This operation is repeated a grejit 
many times before the matrix is worn out. 





OPEN. 



SHUT 



Composition Stamp Handle. 



In the cut, page 115, one number is shown as 
stamped into the soft lead, and at the other end of 
the stamp is a blank space ready for a number. 

The casting of a stamp is so extremely simple 
that no attempt is made to use movable type, as in 
permanent rubber dating stamps. 

While it is obvious that these composition stamps 
could be attached directly to wooden handles, a spe- 



118 IIUBBER HAND STAMP MAKING 

cial style of handle^ shown in the cuts^ is employed 
by the Post Office. A wooden handle carries at its 
end a brass base, to whicli is pivotted a swinging- 
piece that is perforated by a conical oval aperture a 
little larger than the small end of the stamp. The 
edges of tliis aperture are slightly rounded. 

It is swung around as shown in the first figure, 
and the stamp, previously moistened on its sides, is 
forced in. If the stamp is properly made it is sur- 
prising how much force may be used to insert it. If 
the edges of the brass swinging piece ape not rounded 
there is danger of the composition being cut. The 
stamp in its brass frame is then swung back over 
the brass base, where it is secured by a catch. The 
stamp is now ready for use, as shown in the second 
figure of the cut. 

It is imperative that no aqueous or glycerine ink 
be employed for continuous work with such stamps. 
Common printers^ ink is perfectly satisfactory, and 
the work may be nearly or quite as good as that ex- 
ecuted by an India rubber stamp. 

The Post Office manufactures a pad for use with 
printers' ink into whose manufacture the same com- 
position enters. The ink retainer is a piece of fine 
felt, one-quarter to one-half an inch thick. This is 
placed in the bottom of a shallow s-teel mould, where 
it enters for half its depth into a recess that it ac- 
curately fits. The composition from old stamps, 
melted up, is then poured upon and around it, the 
mould being previously oiled. When it is full a 



AND THE MANIPULATION OF liUBBER, 119 

piece of strong manilla paper^ of the area of the felt 
only, is placed upon the bottom of the glue pad on 
its centre, which as it lies in the nionld is its upper- 
most part. The paper adheres strongly as the glue 
hardens. Eventually it is turned out of the m.ould, 
and a pad, shown in the cut, is produced. The 
dotted lines show the limits of the felt pad. The 
glue composition underlies, surrounds and extends 
outwards from the felt portion. It is found that 
the elasticity of the composition makes the pad 




Composition Ink Pad. 



much pleasanter for rapid stamping. 

The above description gives the clew to making 
any stamp of this description. The matrix may be 
of dental plaster, or of oxychloride of zinc cement. 
The mould may be built up of type of any kind. 

The composition is so cheap that the stamp can 
be made quite thick. This gives it a high degree 
of elasticity and adaptability to uneven surfaces. 
It may be mounted by adherence upon a flat board 
or block, provided, if necessary, with handles. If the 



120 RUBBER HAND STAMP MAKING. 

board or block is placed upon the composition while 
it is still Avarm and liquid, as it solidifies tlie board 
and composition will adhere with great tenacity. 

All moulds or surfaces to which it is desired that 
the melted composition shall not adhere must be 
oiled. 

The moulds must not be cold or the composition 
will not enter the fine divisions. If on the other 
hand they are too hot the mixture will adhere. 
Experience will teach the right conditions for suc- 
cess. 

Below are given other formulae for roller composi- 
tion. The formula already given in this chapter is 
that used by the United States Post Office Depart- 
ment. 

I. ^^ Old Home Eeceipt:" Glue 2 lbs., soaked over 
night, to New Orleans molasses 1 gallon. Not 
durable, but excellent while it lasts. 

II. Glue 10)4 lbs., molasses 2^ gal., Venice tur- 
pentine 2 oz., glycerine 12 oz. ; mix as directed 
above. 



CHAPTER XV, 

THE HEKTOGRAPH. 

For obtaining multiple copies of writings the 
apparatus called the Hektograph or Papyrograph 
has been extensively adopted. In general terms it 
consists of a tray filled with a jelly like composition. 
Any imprint made upon the surface with aniline 
ink can be transferred to paper by simple pressure. 
The tray filled with composition is called the tablet. 
It is thus prepared. 

The tray may be made of tin or even of paste- 
board or paper, and should be about one half an 
inch deep. It may be of any size, according to the 
w^ork it is to do. The composition is made from 
the best gelatine and glycerine.- One ounce by 
weight of gelatine is soaked over night in cold water, 
and in the morning the water is poured off, leaving 
the swelled gelatine. Six and one-half fluid ounces 
of glycerine are now heated to about 200 F. (93 C.) 
on a water bath preferably, and the gelatine is added 
thereto. The heating is continued for several hours. 
This operates to expel the water and to give a clear 
glycerine solution of gelatine. 

The composition is then poured into the tray, 



122 RUBBER HAND STAMP MAKING 

which must be perfectly level in order to obtain a 
a surface nearly even with the edge. It is then 
covered so as to keep off the dust. The cover of 
course must not come in contact with the smooth 
surface. In six hours it will be ready for use. 

The original copy that is to be reproduced is 
made upon ordinary paper in aniline ink. One 
formula for the ink reads as follows: Aniline violet 
or blue (2 R B or 3 B) 1 oz., hot water 7 fluid oz.; 
dissolve. After cooling add alcohol 1 fluid oz. 
and glycerine J^ fluid oz.^ a few drops of etlier and 
a drop of carbolic acid. Keep in a corked bottle. 
Other formulae are given in chapter XVII. 

The writing is executed with an ordinary steel 
pen. The lines should be rather heavy so as to show 
a greenish color by reflected light. 

The surface of the pad is slightly moistened with 
a wet sponge and is allowed to become nearly dry. 
The paper is then laid upon it and smoothed down. 
This is best done by placing a second sheet over it 
and rubbing this with the hand. No air bubbles 
must remain between the copy and the tablet^ and 
the paper must not be shifted. 

It is allowed to remain for a minute or less 
and is then raised by one corner and stripped 
from the gelatine surface* It will have left the 
reversed copy of its inscription perfectly reproduced 
upon the tablet. 

At once a piece of ordinary writing paper of the 
desired size and quality is laid upon the tablet, 



AND THE MANIPULATION OF RUBBER. 123 

smoothed down, and stripped off, when it will be 
found to have taken with it a complete copy of 
the inscription or writing. This is repeated over 




The Hektograph. 



and over again with another sheet of paper, until 
the ink on the pad is exhausted. Fifty or more 
good copies can be thus obtained. 

As soon as the work is completed the remains of 
the ink should be washed off Avith a moist sponge 



124 RUBBER HAND STAMP MAKING. 

and the tablet^ after drying a little, will be ready for 
a second operation. 

Some practice is required to ascertain the proper 
strength of the writing and degree of wetness of the 
surface. When the gelatine surface becomes im- 
paired it can be remelted in a water bath if it is iiot 
too dark from absorption of iuk. 

French Ministery of Public Work Formula, — Glue 
100 parts, glycerine 500 parts, finally powdered 
kaolin or barium sulphate 25 parts, water 375 parts. 
Use a little hydrochloric acid in the water for 
washing off the pad after use. 

Hektograph Sheets. — Four parts of glue are soaked 
in five parts of water and three parts of ammonia 
until soft. It is then heated and there is added to 
it three parts of sugar and eight parts of glycerine. 
The mixture is applied to blotting paper. This is 
saturated with it, and successive coats added until a 
smooth surface is produced on one side. This is 
the side for reproduction. It is used like the regular 
tablet except that it is claimed that sponging off 
the waiting is not necessary. Owing to the capillary 
action developed by the blotting paper it is sup- 
posed to be self-cleaning by standing. 



CHAPTER XVI. 

CEMENTS. 

Befoee cementing vulcanized rubber the surface 
^liould be roughened or still better it may be seared 
with a red hot iron. For bicycle tyres this is espe- 
cially to be recommended. 

Cement for Cuts in Bicycle Tyres, Rubber Belts, 
etc. — Carbon bisulphide^ 5 ounces; gutta-percha, 5 
ounces; caoutchouc, 10 ounces; fish glue, 2J^ 
ounces. After it is applied and has dried the 
excess can be removed with a wet knife. Bad cuts 
should first be stitched up. 

Bicycle Tyre Cement to fasten Tyres to Rims. — 
Equal parts of pitch and gutta-percha are melted 
together. Sometimes two parts of pitch are pre- 
scribed. This cement has extended applica- 
tion. 

Cement for Paper Boats and for Mending Rubber 
Goods. — Fuse together equal parts of pitch and 
gutta-percha, and to this add about 2 parts of lin- 
seed oil containing 5 parts of litharge. Continue 
the heat until the ingredients are uniformly com- 
mingled. Apply warm. 

Waterproof Cement. — Shellac, 4 oz; borax, 1 oz; 



126 BUB BEE HAND STAMP MAKING 

"boil in a little water until dissolved, and concentrate 
by heat to a paste. 

Another, — 10 parts of carbon disulphide and one 
part of oil of turpentine are mixed, and as much 
gutta-perclia is added as will readily dissolve. 

Cement for Mending Hard Riibher, — Fuse together 
equal parts of gutta-percha and genuine asphaltum; 
apply hot to the joint, closing the latter immedi- 
ately with pressure. 

Glue to Fasten Leather, etc,, to Metals. — 1 part 
crushed nut galls digested 6 hours with 8 parts dis- 
tilled water and strained. Glue is macerated in its 
own weight of water for 24 hours, and then dis- 
solved. The warm infusion of nutgalls is spread 
on the leather; the glue solution upon the rough- 
ened surface of the warm metal; the moist leather 
is then pressed upon it and dried. 

Marine Glue, Various Formulce, — I. Dissolve 1 
part of india rubber in 12 parts of benzole, and to 
the solution add 20 parts of powdered shellac, heat- 
ing the mixture cautiously over a fire. There is 
great danger of conflagration. Apply with a brush. 

II. Caoutchouc, 1 oz; genuine asphaltum, 2 oz; 
benzole or naptha, q. s. The caoutchouc is first dis- 
solved (as described in chapter XII.), and the 
asphaltum is gradually added. The solution should 
have about the consistency of molasses. 

Cement for Vulcanized India Rubber. — Stockholm 
pitch, 3 parts; American resin, 3 parts; unmixed 
india rubber, 6 parts; oil of turpentine, 12 parts. 



AND THE MANIPULATION OF RUBBEB. 127 

Heat and mix very thoroughly. More oil of turpen- 
tine may be added as required. 

Gutta-Perclia Cement for Leather, — Soak gutta- 
percha in boiling water. Soften in benzole after cut- 
ting up for a day. Heat on a water bath until the 
greater part of the benzole is expelled. When cool 
it will solidify. Use by heating. 

Cement for Rubier Shoes, — 

(1) Chloroform 280 parts. 

India rubber (masticated) 10 '^ 

(2) India rubber 10 " 

Resin 4 *' 

Venice turpentine 2 " 

Oil of turpentine 40 " 

For first solution dissolve by mastication. For 
second, melt the finely divided gum with the resin, 
add the Venice turpentine and finally the oil of tur- 
pentine. Use heat if necessary. Mix both solu- 
tions finally. To apply, saturate a piece of linen 
with the cement and apply to the spot previously 
coated with the cement. As it dries apply a little 
more as required. A finishing varnish is given in 
the last chapter. Parkes^ cold curing process may 
be applied as described in chapter XL 

Chatterton's Compound for uniting sheets of 
gutta-percha in cable cores and for general work 
with gutta-percha coated wires. — Stockholm tar, 
] part; resin, 1 part; gutta-percha, 2 parts. 

Waterproofing for Wooden Battery Cells, — Resin, 
4 parts; gutta-percha, 1 part; boiled oil, a little. 



128 BUBBEB HAND STAMP MAKING. 

A7iother Fonmila. — Burgundy pitch, 150 parts; 
old gutta-percha in fine shreds, 25 parts; ground 
pumice stone, 75 parts. Melt the gutta-percha and 
rnix with the pumice stone and then add the pitch, 
melting all together. Apply melted and smooth off 
with a hot iron. 

Cement for Oelluloid. — Shellac, 1- part is dissolved 
in spirits of camphor 1 part, with 3 to 4 parts stro^ig 
alcohol. It is applied warm and the parts united 
must not be disturbed until the cement is hard. 



CHAPTER XVIL 

INKS. 
RUBBEK STAMP UiK, 

Aniline blue soluble, IB 3 parts. 

Distilled water 10 " 

Acetic acid 10 '' 

Alcohol 10 '' 

Glycerine 70 



iC 



For other colors the following aniline colors may 
be substituted in proportions given: 



Methyl violet, 3 B (violet) 3 parts. 

Diamond f uchsin I, (red J , 2 '' 

Methyl green yellowish 4 ^* 

Yesuvin, B (brown) 5 " 

IS^igrosin, W (blue black) 4 " 

For very bright red 3 parts of Eosin BBN". are 
used. In this case the acetic acid must be omitted. 
In all cases the colors should first be rubbed up 
with the water in a mortar^ and the glycerine 
should be added gradually. These inks will answer 
for the hektograph. 

Hektograph Ink. — Aniline color^ 1 part; water, 7 
parts; glycerine, 1 part. A little alcohol may be 



130 BUBBER HAND STAMP MAKING 

used with advantage to dissolve the aniline color. 
It can be expelled by heating if it proves objection- 
able. 

Aniline Ink Vehicle,— F rot, E. B. Shuttlevvorth^ 
of Toronto^ Ont.^ suggests the use of castor 5il in 
place of vaseline and other veliicles for typewriter 
ink. The aniline colors may lirst be dissolved in 
alcohol, and the solution may be added to the oil. 
They may also be dissolved directly in the oil in 
which most of them are soluble. 

Indelible Stamping Inks, — I. Asphaltum, 1 part; 
oil of turpentine, 4 parts; dissolve and temper with 
printer^s ink. The ink may be omitted, and solid 
dry color added. 

II. Sodium carbonate, 22 parts; glycerine, 85 
parts; dissolve and rub up in a mortar with gum 
arable, 20 parts. In a separate vessel dissolve silver 
nitrate, 11 parts; in officinal aqua ammonia, 20 
parts. Mix the two solutions, and heat to the boil- 
ing point, 212° F. (100° C). After it darkens, add 
Venice turpentine, 10 parts. After applying to the 
cloth, a hot iron should be applied^ or it should be 
exposed to the sun. 

III. Dr. W. Reissig^s formula: 



Boiled linseed oil varnish 16 parts. 

Finest lamp black 6 '' 

Ferric chloride (sesquichloride of 

iron) 2 to 5 '' 



AND THE MANIPULATION OF RUBBER, 131 

Dilute a little for use with varnish. After this 
ink has been removed^ no matter how completely it 
can be detected by dipping the paper into a solution 
of ammonium sulphide. 

IV. 

Aniline black in crystals 1 part. 

Alcohol 30 " 

Glycerine 30 " 

Dissolve in the alcohol^ and add the glycerine 
afterwards. 

Shoto Card LiTc. — 

Pure asphaltum 16 parts. 

Venice turpentine 18 '' 

Lamp-black 4 ^' 

Oil of turpentine 64 '^ 



Dissolve the asphaltum in the turpentine^, and 
thoroughly mix. 

Stencil Ink, — Shellac^ 2 ounces; borax^ 2 ounces; 
water^ 25 ounces. Dissolve by heat if necessary, 
first the borax alone, and then adding the shellac. 
To the clear solution add gum arable, 2 ounces. 
Color with lamp-black, with Venetian red, or with 
ultramarine, to suit the taste. Another formula 
gives shellac, 4 parts, borax, 1 part, and omits the 
gum arable. 

Copying Inh (for use without a press by simply 
pressing and rubbing with the hand), by Prof. Att- 
field, P.R. S. — Use ink of any kind of extra strength. 



132 RUBBER HAND STAMP MAKING 

This in many cases can be made by evaporating 
common ink down to six tenths of its volume. 
Then mix with it two thirds of its volume of glycer- 
ine, so as to restore the original volume. 

WJiite Inh, — Barium sulphate, or ^^ flake white ^^ 
is mixed with gum arable water of sufficient thick- 
ness to keep it suspended, at least while in use. 
Starch or magnesium carbonate or other white pow- 
der may be used instead of the barium sulphate. 
The powder must be of impalpable fineness. 

White Ink on Blue Pay ^^.,:—k. solution of oxalic 
acid in water is used for this purpose. It may be 
applied with a rubber stamp or with a common pen. 
A quill or gold pen is the best as a steel pen is soon 
corroded. The ink bleaches the paper wherever it 
touches it, giving white lines on a blue ground. 

Gold Inh. — Gold leaf with honey is ground up in 
a mortar, best an agate mortar, or on a painters^ 
slab with a muller. It is added to water, and thor- 
oughly mixed and at once poured off from the first 
sediments, filtered out, and washed. This is done to 
secure the impalpably finely ground gold only. 
The resulting powder is mixed with a suitable vehi- 
cle, such as white varnish or gum arable water. 

Silver Inh, — As above, using silver leaf. 

Zinc Lahel Ink. — I. Verdigris,. 1 part; ammo- 
nium chloride, 1 part; lamp-black, | part; water, 10 
parts. 

II. Platinum bichloride, 1 part; gum arable, 1 
part; water, 10 parts. 



AND THE MANIPULATION OF RUBBEB. 133 

Diamond Inh for Etching Glass, — This consists 
essentially of hydrofluoric acid mixed with barium 
sulphate to the consistency of cream. The barium 
sulphate is quite inoperative except as giving a body 
to prevent the ink from spreading. It is applied 
with a rubber stamp or pen and allowed to remain 
for ten minutes or until dry. On removal of the 
white powder, the design will be found etched on the 
glass. The following is a formula for it. 

Saturate hydrofluoric acid with ammonia, add an 
equal volume of hydrofluoric acid and thicken with 
barium sulphate in fine powder. 



CHAPTER XVIIL 

MISCELLANEOUS. 

To Soften and Restore India Rubber Hose, etc, — I. 
Dip in petroleum and hang up for a couple of days. 
Eepeat process if necessary. 

II. The above process is applicable to all articles, 
but is specified for hose. It is stated that old rub- 
ber that has become hard may be softened by expos- 
ure first to vapor of carbon disulphide^ followed by 
exposure to the vapor of kerosene. The latter vapor is 
found to be a general preservative for india rubber. 

III. Dr. Pol recommends immersion in a solution of 
water of ammonia, 1 part, and water 2 parts, from a 
few minutes to an hour. 

To Prevent Decay of Rubier Tubing. — The decay 
of rubber tubing has been attributed to the forma- 
tion of sulphuric acid from the sulphur mixed 
with it. M. Ballard has suggested washing with 
water or weak alkaline solution five or six times in 
a year. 

Joints between India Rubber Tubing and Metal. — 
Where tubing is temporarily slipped over metal gas 
pipes and similar connections, as in the chemical lab- 
oratory, it is well to apply glycerine to the metal. 



THE MANIPULATION OF BUB BEE. 135 

It acts as a lubricant in slipping the tubing on^ and 
assists in its withdrawal. 

Preservmg Vulcmiite, — Wash occasionally with a 
solution of ammonia and rub with a rag slightly 
moistened with kerosene oil. 

Effect of Copper upon Rubber, — In a paper read be- 
fore the recent meeting of the British Association, 
Sir William Thomson stated that metallic copper, 
when heated to the temperature of boiling water, in 
contact with the rubber, exerted a destructive effect 
upon it. With a view to finding whether this was 
due to the copper jt?er se, or to its power of conduct- 
ing heat more rapidly to the rubber, he laid a sheet 
of rubber on a plate of glass, and on it placed four 
clean disks, one of copper, one of platinum, one of 
zinc and one of silver. After a few days in an incu- 
bator at 150° F., the rubber under the copper had be- 
come quite hard, that under the platinum had be- 
come slightly affected and hardened at different 
parts, while the rubber under the silver and under 
the zinc was quite hard and elastic. This would 
w^arrant the inference that the metallic copper had 
exerted a great oxidizing effect on the rubber, the 
platinum had exerted a slight effect, while the zinc 
and silver respectively had no injurious influence on 
it. The rubber thus hardened by the copper con- 
tained, strange enough, no appreciable trace of cop- 
per; the copper, therefore, presumably sets up the 
oxidizing action in the rubber without itself perme- 
ating it. 



186 RUBBER HAND STAMP MAKING 

Gas Tight Tubings, — Fletcher has invented a gas 
tight rubber tubing in which a layer of tinfoil is in- 
terposed between two concentric rubber tubes^ all 
vulcanized together. 

Printing Colors upon India Rniber, — It may some- 
times be desirable to have a surface of vulcanized In- 
dia rubber so prepared that it will take colors such as 
are used for calico printing. This end is simply at- 
tained by sprinkling the article with farina before 
vulcanizing. A small quantity attaches itself and 
forms an excellent base for color printing. 

Gutta-PercUa for Coating Glass, — For focusing 
glass in photography and for similar purposes where 
ground glass or a translucent material is required, 
a solution of gutta-percha in chloroform is highly 
recommended. This is flowed over or painted on 
the glass and is allowed to evaporate afterwards. 

Burned Rubber, — A very soft pure gum sold for 
artists^ use is improperly termed burned rubber. It 
is used in crayon work for removing and lightening 
marks by dabbing it against the paper, cleaning the 
rubber from time to time. It is so soft that it picks 
up and removes crayon marks without the necessity 
of friction. Thus the rubbing out or more properly 
erasing operation can be localized and crayon tints 
can be lightened in tone without impairment or 
^^ smutting.'^ It is a very elegant accessory to the 
artists^ paraphernalia. To make it, pure virgin gum, 
preferably the best Para, is cut into pieces and soaked 
for some hours in benzole. A long soaking is ad- 



AND THE MANIPULATION OF RUBBER. 137 

visable. The pieces are then removed from the ben- 
zole and are ground in a mortar until perfectly hom- 
ogeneous. The mass is gathered up with a spatula 
and is pressed into little tin boxes. If desired it 
may be dried upon a water bath. This is not nec- 
essary as^ if the box is left open, it will rapidly season 
itself. It should be very soft, should tend to adhere 
to the fingers, yet should leave them easily, and 
should strip cleanly from the box. A very little 
turpentine makes it more adhesive. It may even 
be softened in turpentine alone. This gives a gum 
that seasons more slowly and is in some respects pref- 
erable to the benzole made preparation. It is sold 
at a high price by the dealers, as the demand for it is 
limited. 

Rnhber Sponge, — This is also an artistes rubber. 
It is also used for cleaning kid gloves. It is made 
by incorporating with the masticated or washed and 
sheeted gum any material or materials that will give 
off vapor in the curing process. Damp sawdust and 
crystallized alum are used as giving off vapor of 
water or steam, or ammonium carbonate as giving 
off vapors of ammonia carbonic acid gas and steam. 
The mixed gum may be cured in moulds, which it 
will fill by its expansion. 

Shellac Varnish for India Rubier, — This is made 
by soaking powdered shellac in ten times its weight 
of strong aqua ammonia (26"^ B.). At first no 
cliange beyond a coloring of the solution is percep- 
tible. After many days standing the bottle, which 



138 IWBBER HAND STAMP MAKING 

should have a glass stopper^ being tightly closed, 
tlie shellac disappears, having entered into solution. 
It may be a montli before complete solution. This 
forms an excellent varnish for India rubber shoes 
and similar articles. It may be applied with a rag. 
It is also a good application for leather iu some 
cases and doubtless many other uses could be 
made oi it. It would act well as a vehicle for a 
dark pigment such as lamp-black. It will reju- 
venate a pair of india rubbers very nicely. The 
ammonia exercises also a good influence on the rub- 
ber. It has been recommended as a cement for 
attaching rubber to metal, but its adhesive powers 
are not always satisfactory. 

Simple Siihstitute for Stamps. — A very simple 
though rough and imperfect substitute may be 
made by gluing with common carpenter^s glue 
pieces of thick string upon a piece of wood, the 
string being given the form of the desired letters. 
Care must be taken to avoid saturating and stiffen- 
ing the string with the glue. 

India Rubber SitbstitiUes, — One of these under 
the name of vulcanized oil is thus described by 
Bolas: 

^' Vulcanized oil is, perhaps, of more interest, and 
many oils, such as linseed and others resembling it, 
may be vulcanized by being heated for some time to 
150° Centigrade, with twelve to twenty per cent, of 
sulphur. The product obtained is soft, and some- 
what resembles very bad india rubber. By increas- 



AND THE MANIPULATION OF BUB BEE. 139 

ing the proportion of sulphur very much indeed^ say 
to four times the weight of the oil^ and vulcanizing 
at a higher temperature^ a hard substance^ resem- 
bling inferior vulcanite^ is obtained. 

'^'^Soft and hard vulcanized oil have been intro- 
duced into commerce at various times and under 
many names; but these materials never seem to 
have made very much headway/^ 

Another method of treating the oil consists in 
mixing it with a solution of chloride of sulphur in 
carbon disulphide or in naptha. On standing, the 
volatile solvents escape, leaving a thick mass, which 
is the substitute. 

In combinations of aluminum with the fatty 
acids, forming aluminum soaps, and of these, alu- 
minum palmitate especially, a substitute for India 
rubber has been sought but without success. 

Metallized Caoutclioitc. — Unvulcanized gu m is 
mixed with powdered lead, zinc, or antimony. The 
mixed India rubber is then cured as in the regular 
process. 

EMEEY WHEELS A^J) WHETST0:N"ES. 

Bolas thus describes their manufacture: 
'• When ordinary vulcanized rubber is heated to 
230° Centigrade, (446° F.) or until it melts, a per- 
manently viscous product is obtained, and this sub- 
stance, if mixed with emery and sulphur to a kind 
of paste, forms a material out of which the so-called 
agglomerated emery wheels or grinders may be 



140 RUBBER HAND STAMP MAKING 

formed, the mixed materials being next hardened or 
cured by the application of a steam heat. Emery 
wheels and hones made on this principle were intro- 
duced by Deplanque about twenty-three years ago. 

^^ Thirty-five parts of old vulcanized caoutchouc 
having been placed in a kind of still, heat is appli(^d 
to melt it, the operation being assisted by the grad- 
ual addition of about ten parts of heavy coal oil; 
but this latter is afterward distilled off. The soft- 
ened caoutchouc is then incorporated with 500 parts 
of emery of the required degree of fineness and 
nine parts of sulphur. These materials having 
been thoroughly mixed, the hones or wheels are 
manufactured, and afterward cured or baked at a 
heat of 140° Centigrade, (284° F.) during a period of 
about eight hours. Grinding wheels, made in the 
above manner, can be worked at a speed of 2,000 
revolutions per minute, and are extremely useful 
for the working of hardened steel or other obdurate 
materials.^'' 

EtcJiing on Metals and Glass, — India rubber stamps 
can be used for placing the ground upon knife 
blades and similar articles which are to be etched. 
The parts untouched by the stamp are attacked by 
the acid. In the case of glass, diamond ink (page 
133) can be put on with a stamp. The acids for 
metal etching might be thickened with barium 
sulphate also and applied in the same way. In these 
cases the inscription of the stamp would be etched. 
Where ground is put on, whether on glass or 



AND THE MANIPULATION OF BUBBEB. 141 

metal, the design for the stamp will be pro- 
tected. 

Etching Ground for Metals. — Equal parts of as- 
phalt. Burgundy pitch and beeswax melted together 
and mixed thoroughly. It may be softened with 
mutton suet. Beeswax may be used, dissolved in 
ether or simply melted. Yellow soap is sufficient 
for ordinary work. 

Etching Solutions for Biting %n. — For steel and 
iron, a, sulphate of copper and common salt in solu- 
tion, b, sulphate of copper, sulphate of alumina, 
and common salt, of each two drachms; acetic 
acid, 1% oz. c, sulphuric acid, diluted with five vol- 
umes of water with a little sulphate of copper. 
For other metals, except gold and platinum, nitric 
acid diluted with five volumes of water. 

Etching Ground for Glass, — Melted beeswax is 
generally recommended. It can be removed with 
spirits of turpentine after as much as possible has 
been scraped off. 

Etching Glass, — Glass may be conveniently etched 
by exposing it to the vapor of hydrofluoric acid. 
A shallow leaden tray, as large as the glass, is re- 
quired. A quantity of fluorspar is placed in it and 
is moistened with concentrated sulphuric acid. The 
glass is placed face downward over the tray. It is 
supported over the mixture by resting on the 
edges of the tray or by any simple method, and the 
whole is covered with a towel. In half an hour or 
more the etching will be completed. The vapors 



142 RUBBER HAND STAMP MAKING. 

must not be allowed to escape into any room con- 
taining glass or metal articles as they corrode every- 
thing. Great care should be taken also not to let 
the mixture touch the hand, as painful ulcers are 
the result, 

India Ruhher Shoe Blacking, — Eaw india rubber 
is given as a constituent of several shoe blackings. 
Formulae are given as below for paste and liquid 
blackings. 

I. Paste blacking: bone-black, 20 parts; molasses, 
15 parts; vinegar, 4 parts; sulphuric acid, 4 parts; 
caoutchouc oil (as given below), 3 parts. 

II. Liquid blacking: bone-black, 60 parts; mo- 
lasses, 45 parts; gum arable dissolved in water, 1 
part; vinegar, 50 parts; sulphuric acid, 24 parts; 
caoutchouc oil, 9 parts. 

Caoutchouc oil is made by dissolving or digesting 
virgin rubber 55 parts in linseed oil 450 parts. 

Waterj^roof Composition for Boots, — One ounce of 
virgin rubber cut into pieces is digested in enough 
oil of turpentine to form a stiff paste. In applying 
heat take great care lest the contents of the vessel 
become ignited. When homogeneous, which con- 
dition maybe brought about by rubbing in a porce- 
lain mortar, as described in chapter XII., it is mixed 
'with 5-6 ounces of boiled linseed oil. This gives, 
an ointment almost of the consistency of butter. 



INDEX, 



PAGE 

Absorption of sulphur process.. loo 
Absorption of water by india 

rubber 31 

Africa, ways of collectings rub- 
ber sap 15-17 

Analysis of sap of india rubber 

tree 27 

-Apparatus for stamp making. 61-63 
Artists' burned rubber 136-137 

Balloons 95 

Bands, india rubber 41 

Bicycle tyre cement 125 

Blacking, india rubber 142 

Borax and water solution of 

rubber 106-107 

Brazil, ways of collecting sap. 20-21 

Bromine as vulcanizer 100 

Bulbs, how made 92-93 

Burned rubber, artists' 136-137 

Calendering , 43 

Cane tips 90 

Caoutchin 30 

Caoutchoucin ^ 30 

Caoutchouc, (see India Rubber.) 

Cements 125-128 

Clamp for vulcanizing press 52 

Cohesion of rubber, its impor- 
tance to the manufacturer.. 26-27 
Cold curing 100-102 



PAGE 

Composition for stamps and its 

moulding 1 13-120 

Composition inking pad 118-119 

Composition stamp handle . . 117-118 

Cord, rubber 92 

Corks 90-91 

Curing 44 

Curin^, how to judge of com- 
pletion of... ,. .. 70 

Curing in liquid bath , 97 

Curing in sulphur bath 99 

Curing, temperature of 58 

Central America, ways of col- 
lecting rubber 18-19 

Chair leg tips 90 

Chalk plates 83-84 

Chlorine as vulcanizer 100 

Chloroform as a solvent 105 

Coagulation of sap by a plant. . . 19 

Coagulation of sap by alum 22-23 

Coagulation of sap by fire 21-22 

Coagulation of sap by salt 18 

Cohesion of pure rubber 25 

Dating stamps, composition. 116-117 
Didot's polytype for matrices.. 82-83 
Distillation products of india 

rubber 29-30 

Dolls, how made 92-93 

Ebonite 108-111 

Ebonite, polishing iio-m 



144 



INDEX 



Emery wheels and whetstones 

139 140 

Emulsion of caoutchouc 10 

Etching 140-142 

Fins, removal of 86 

Flask for type moulding 74 

Flong matrices 80-82 

Flong paste 80 

Fluid for mixing with plaster 
for matrices 55 

Gas heated steam vulcanizer. ... 53 

Glue, marine .. 126 

Glue stamps 113-120 

Glycerine bath for curing 97 

Goodyear, Charles 13-14 

Gutta-percha 111-112 

Gutta-percha, moulding 111-112 

Gutta-percha, vulcanizing 1 1 1 

Hektograph, composition 

121-122, 124 

Hektograph, how made and 

used 121-124 

Hektograph ink (also see inks).. 121 
Hektograph sheets 124 

India Rubber, absorption of 

water by 31 

India rubber, African 15-17 

India rubber, artists' burned 136-137 
India rubber, availability for 

small articles 85 

India rubber, cohesion of unvul- 

canized , 25 

'India rubber, composition of 27 

India rubber, discovery of, etc. 11-13 
India rubber, effects of temper- 
ature on 28-29 

India rubber, elasticity of 

India rubber sap, its coagula- 
tion II 



India rubber sheet, how made. . 40 
India rubbers, original way of 

making 10 

India rubber stam'p making with- 
out apparatus 71 

India rubber stamps, home-made 

mould 48-50 

India rubber stamps, starting 

point 47 

India rubber, trees producing.. 9 
India rubber tree sap, analysis of 27 

India rubber type 73 

India rubber, vulcanized, general 

properties of 32-33 

India rubber, where collected, 11 
India rubber, inelastic, how 

made ... 31 

India rubber, its mastication. . 38-40 
India rubber, manufacture of, 35-46 
India rubber, necessity of dry- 
ing. 38 

India rubber, points to be fol- 
lowed in moulding small arti- 
cles 85 

India rubber, preliminary opera- 
tions in manufacturing 35-36 

India rubber, preservimg, etc. 134-135 
India rubber, properties of .... 28 

India rubber sap 9-11 

India rubber stamp vulcanizing 58-60 
Inelastic state of India rubber.. 31 
Inks, special for stamping,etc. 129-133 
Iodine and haloid vulcanizers. . . 100 
Isoprene 30 

Leaves, skeletonized as models. 92 
Liquid bath curing 97 

Machine for cutting sheet and 
threads 40 

Machine for making mixed 
sheet 42-43 



INDEX. 



US 



Machine for masticating 38-40 

Machine for washing and sheet- 
ing 37 

Mackintosh 13 

Mackintoshes, how made 45-46 

Marshmallow not for mixture 

with plaster 57 

Masticated rubber, its easy solu- 
tion... ' 103-104 

Masticating in mortar with ben- 
zole 103-104 

Mastication of rubber 38-40 

Materials mixed with india 

rubber 43 

Matrices, various kinds of, for 

stamps . 80-84 

Matrix for stamp-making. .. 54-55 

Matrix making by casting 56-57 

Matrix press 56 

Matrix, process of making, for 

stamps 54-55 

Mats 91-92 

Metals, welding and cohesion 

of 25-26 

Miscellaneous .. 134-142 

Mixed sheet 42-44 

Mixed sheet for stamps 47-48 

Mould, home-made for stamps. 48-50 
Moulding and curing stamps. . 58-60 
Moulds for composition stamps, 

temperature of 120 

Moulds, material for 86 

Naptha and volatile solvents, 
danger of ■ 107 

Naptha, solvent 104-105 

Nicaragua, ways of collecting 
sap 19-20 

Nitric acid as vulcanizer 100 

Oil for composition stamp 
moulds iig-120 



Oil for mould face 55 

Oils fixed bad effect on solu- 
tions .... 105 

Oxychloride of zinc cement for 
matrices 57 

Papier mache matrices 80-82 

Paraffin and rubber 105-106 

Parkes' process 100-102 

Payen's solvent 105 

Pencil aps, moulds for 89-90 

Phenyle sulphide as softener of 

vulcanized rubber. , 106 

Plaster dental for matrices ..... 54 
Press for moulding stamps, etc. 

51-52 

Press, gas-heated 52-53 

Press, home-made 49 

Press, matrix making 55-56 

Products, general division of.. 35-36 

Rods, stirring for laboratory. . . 95 

Rubber, origin of name 12 

Rubber, see India Rubber 

Salt bath for curing 98 

Sap of india rubber tree, analysis 
of 27 

Sheeting and washing 37-38 

Sheet rubber, how made 40 

Sheet rubber, its joining 94 

Shellac for strengthening matrix 

Shoes, blacking for 142 

Shoes, india rubber, cement for. 127 

Siphonia, origin of name 11 

Solution, different views of. . . 31-32 

Solution, difficulties of 103 

Solvents for rubber 104-105 

Spring chase for matrices 56 

Springs for stamp moulds 51 

Springs on moulding press ...... 51 

Sponge india rubber 137 

Stamp making 47 



146 



1N1)E2:. 



Stamps, rubber, substitute for. 138 

Stamps, see India Rubber, Com- 
position and general titles. 

Strauss' method of coagulating 
sap . . . .» 22-23 

Suction discs, regular mould for 



88-^ 



Suction discs, simple mould for 

87-88 

Sulphides, alkaline as vulcaniz- 

ers 100 

Sulphur, absorption process... 100 
Sulphur bath for mixing and 

curing 98-100 

Sulphur chloride process. . . . 100-102 
Sulphur, how mixed with gum.. 43 
Sulphur, its escape from vulcan- 
ized rubber 33-34 

Sunlight excluded from washed 

sheet rubber 38 

Syringes made by Indians 11 

Test for curing with knife 48 

Thread, rubber, cut 41 

Thread, rubber, moulded 92 

Tissues, coated, how made 45-46 

Tubes, connecting glass. 96 

Tube, seamless 92 

Turpentine, a solvent for vulca- 
nized rubber. 106 

Turpentine compared with 

caoutchoucin 30 

Turpentine, viscid nature of 

solution 104-105 

Type, india rubber 73 



Type moulding flask 74 

Type and stamps from vulca- 
nized rubber 77 

Type, cutting apart 75 

Type, points in moulding 75 

Type, quads, and spaces for 

stamp models 71-72 

Type, steel moulds for 76 

United States composition 
stamps 1 13-120 

Varnish shellac for india rub- 
ber 137-138 

Vulcanite 108-111 

Vulcanization, its two steps 42 

Vulcanization, steps in pro- 
cess 47-48 

Vulcanized rubber stamps and 

type 77 

Vulcanizer 52-53 

Vulcanizer, fish kettle as a. . . 69-70 

Vulcanizer, flower pot 68-70 

Vulcanizer, chamber 63 

Vulcanizing and moulding 
stamps 58-60 

Washing and sheeting 37-38 

Water absorbed by india rubber. 31 
Waterproof composition for 

shoes 142 

Waterproofing for battery 

cells 127-128 

Zinc, chloride ., 57 



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MECHAHICAL MOVEMEHTS, 

POWERS, DEVICES, AND APPLIANCES. 

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siicor^D Hi>ixior«. 




— BY — 
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JUST PUBLISHED. 



Second Edition^ Revised and Much Enlarged* 

Gas, Gasoline and Oil Engines. 

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LARGE OCTAVO. 384 PAGES. PRICE, $2.50. 



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A FEW EXTRACTS OF NOTICES FROM THE PRESS. 

This book is written in a plain, concise style, whieh will commend it to practical men. 
— CoUiery Engineer. 

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Mr. Hiscox's work, devoted to American practice, is practically unique in subject, 
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*ti*G<^ies of above book prepaid to any address on receipt of prioe. 



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APR 14 



